Common Weakness Enumeration

CWE-79

Allowed

Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

Abstraction: Base · Status: Stable

API response cwe.mitre.org

The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.

68240 vulnerabilities reference this CWE, most recent first.

GHSA-QFRW-5RXM-MHH2

Vulnerability from github – Published: 2026-07-20 21:35 – Updated: 2026-07-20 21:35
VLAI
Summary
Mistune renderers/html.safe_url: HARMFUL_PROTOCOLS list misses legacy and chained schemes that historically chain to `javascript:` execution
Details

Summary

Type: URL-scheme allowlist gap. The safe_url filter only blocks the four schemes javascript:, vbscript:, file:, data:. Several other schemes are accepted into rendered <a href="..."> and <img src="..."> tags despite being known XSS vectors in legacy or chain-handling browsers. The same gap applies to direct links, reference links, and autolinks. File: src/mistune/renderers/html.py, line 11-23 (HARMFUL_PROTOCOLS list). Root cause: the HARMFUL_PROTOCOLS tuple is a hardcoded, opt-out denylist of four entries. Browsers historically supported (and some still partially support) several other schemes that either execute JavaScript directly (livescript:, mocha:) or wrap a javascript: payload (feed:javascript:, view-source:javascript:, jar:javascript:, ms-its:javascript:, mk:@MSITStore:javascript:). On user-agents that still recognise these schemes (older Firefox builds for feed:/jar:, all Internet Explorer / Edge Legacy for ms-its:/mk:/res:, niche chrome-style browsers, browser extensions that register custom protocol handlers), clicking a link rendered by mistune executes attacker-controlled JavaScript in the page's origin.

Affected Code

File: src/mistune/renderers/html.py, lines 10-62.

class HTMLRenderer(BaseRenderer):
    HARMFUL_PROTOCOLS: ClassVar[Tuple[str, ...]] = (
        "javascript:",
        "vbscript:",
        "file:",
        "data:",
    )                                                         # <-- BUG: incomplete denylist
    GOOD_DATA_PROTOCOLS: ClassVar[Tuple[str, ...]] = (
        "data:image/gif;",
        "data:image/png;",
        "data:image/jpeg;",
        "data:image/webp;",
    )

    def safe_url(self, url: str) -> str:
        if self._allow_harmful_protocols is True:
            return escape_text(url)
        _url = url.lower()
        if self._allow_harmful_protocols and _url.startswith(tuple(self._allow_harmful_protocols)):
            return escape_text(url)
        if _url.startswith(self.HARMFUL_PROTOCOLS) and not _url.startswith(self.GOOD_DATA_PROTOCOLS):
            return "#harmful-link"
        return escape_text(url)                               # <-- BUG: any scheme not in HARMFUL_PROTOCOLS passes through

Why it's wrong: an opt-out denylist for URL schemes is the wrong shape. The set of schemes a user-agent might honour is unbounded (registered handlers, browser extensions, OS-level protocol registrations, custom intent handlers on Android, etc.), but the set of schemes a markdown renderer needs to allow is small (http://, https://, mailto:, optionally tel:, ftp:, fragment-only #anchor, and a few image-only data: types). Switching to an opt-in allowlist with a safe_extra_protocols knob for callers who need others would close every variant of this bug class permanently. The current code accepts every chained-scheme XSS vector for as long as the project remembers to keep the denylist current.

Exploit Chain

  1. Application accepts attacker-supplied markdown and renders it with mistune. The default escape=True prevents raw HTML, but link href/image src filtering is the only XSS defense for [click](...) and ![alt](...) syntax.
  2. Attacker writes [click here](feed:javascript:alert(document.cookie)). mistune's safe_url checks feed:javascript:alert(document.cookie) against HARMFUL_PROTOCOLS = ('javascript:', 'vbscript:', 'file:', 'data:') — none match. The href is escape_text'd (HTML-entity escape) and emitted as <a href="feed:javascript:alert(document.cookie)">click here</a>.
  3. Victim using a Firefox build that still has the feed handler registered (extension, configuration, or LTS that retained the feed reader past the 64.0 removal — including some forks and ESR builds) clicks the link. Firefox's feed handler invokes the inner URL, which is javascript:alert(...). JS executes in the page's origin. Victim's session cookie is exfiltrated.
  4. Same pattern for livescript:alert(1) (Netscape Communicator era, still recognised by some niche browsers / browser-emulator tools), view-source:javascript:alert(1) (Firefox, see CVE-2009-1938), jar:javascript:alert(1) (older Firefox), ms-its:javascript: (IE/Edge Legacy), res:javascript: (IE), mk:@MSITStore:javascript: (IE CHM viewer). Each user-agent that recognises one of these is exploitable; the user-agent population that recognises at least one is not negligible (corporate environments still running Edge Legacy compatibility mode, locked-down kiosk browsers, Android WebView in apps that register custom intent handlers, Linux distros with old Firefox ESR plus the feed: extension, etc.).

The same primitive applies to image src (![](feed:javascript:...) rendered as <img src="feed:...">) — though most browsers don't fetch javascript: from img src, the same chained handler quirk applies on a few user-agents — and to reference links and autolinks (verified in the PoC below; the rendered HTML is identical regardless of which markdown link syntax is used).

Security Impact

Severity: sec-moderate. Conditional XSS depending on user-agent. Modern Chrome / Edge Chromium / Safari ignore most of these schemes, but Firefox forks, Edge Legacy, in-app WebViews, browser extensions registering custom handlers, and corporate browser deployments are exposed. Defence-in-depth is the framing: a markdown renderer should not need to track which browsers still honour which legacy chained-scheme. Attacker capability: plant a link in any place the application renders user-supplied markdown. When clicked by a user-agent that honours the legacy scheme, the attacker's JavaScript runs in the page's origin (steal cookies, perform actions as the victim, etc.). Preconditions: application uses mistune to render attacker-influenced markdown. Default config. Victim user-agent is one of the affected populations. No specific mistune option is required. Differential: PoC-verified against mistune@3.2.1, default config. The following inputs all PASS the filter and reach the rendered HTML unchanged:

import mistune
md = mistune.create_markdown()
for url in [
    'feed:javascript:alert(1)',                  # Firefox feed handler chain
    'livescript:alert(1)',                       # Netscape, niche browsers
    'mocha:alert(1)',                            # Netscape, niche browsers
    'view-source:javascript:alert(1)',           # Firefox view-source chain (CVE-2009-1938 class)
    'jar:javascript:alert(1)',                   # Firefox jar: handler chain
    'ms-its:javascript:alert(1)',                # IE/Edge Legacy InfoTech Storage handler
    'mk:@MSITStore:javascript:alert(1)',         # IE CHM viewer chain
    'res:javascript:',                           # IE resource: handler
]:
    print(md(f'[click]({url})').strip())

# Output (each one passes the filter):
#   <p><a href="feed:javascript:alert(1)">click</a></p>
#   <p><a href="livescript:alert(1)">click</a></p>
#   <p><a href="mocha:alert(1)">click</a></p>
#   <p><a href="view-source:javascript:alert(1)">click</a></p>
#   <p><a href="jar:javascript:alert(1)">click</a></p>
#   <p><a href="ms-its:javascript:alert(1)">click</a></p>
#   <p><a href="mk:@MSITStore:javascript:">click</a></p>
#   <p><a href="res:javascript:">click</a></p>

For comparison, the four schemes already in the denylist are correctly blocked: javascript:, vbscript:, file:, data:text/html all return <a href="#harmful-link">.

The same gap applies to reference links ([click][ref]\n\n[ref]: feed:javascript:alert(1) → <a href="feed:javascript:alert(1)">) and to autolinks (<feed:javascript:alert(1)> → <a href="feed:javascript:alert(1)">).

Suggested Fix

Switch from denylist to allowlist. The set of schemes a markdown renderer needs to allow is small and well-known; the set of schemes that might trigger handler chains is unbounded.

--- a/src/mistune/renderers/html.py
+++ b/src/mistune/renderers/html.py
@@ -7,21 +7,28 @@ class HTMLRenderer(BaseRenderer):

     _escape: bool
     NAME: ClassVar[Literal["html"]] = "html"
-    HARMFUL_PROTOCOLS: ClassVar[Tuple[str, ...]] = (
-        "javascript:",
-        "vbscript:",
-        "file:",
-        "data:",
-    )
+    SAFE_PROTOCOLS: ClassVar[Tuple[str, ...]] = (
+        "http:",
+        "https:",
+        "mailto:",
+        "tel:",
+        "ftp:",
+        "ftps:",
+        "irc:",
+        "ircs:",
+    )
     GOOD_DATA_PROTOCOLS: ClassVar[Tuple[str, ...]] = (
         "data:image/gif;",
         "data:image/png;",
         "data:image/jpeg;",
         "data:image/webp;",
     )

@@ -49,15 +56,21 @@ class HTMLRenderer(BaseRenderer):
     def safe_url(self, url: str) -> str:
-        if self._allow_harmful_protocols is True:
-            return escape_text(url)
-
-        _url = url.lower()
-        if self._allow_harmful_protocols and _url.startswith(tuple(self._allow_harmful_protocols)):
-            return escape_text(url)
-
-        if _url.startswith(self.HARMFUL_PROTOCOLS) and not _url.startswith(self.GOOD_DATA_PROTOCOLS):
-            return "#harmful-link"
-        return escape_text(url)
+        # Allow-list: only schemes in SAFE_PROTOCOLS, image-only data: URLs in
+        # GOOD_DATA_PROTOCOLS, scheme-relative URLs (//host/path), absolute
+        # paths (/path), and anchor-only references (#fragment) reach the
+        # rendered output. Everything else is replaced with '#harmful-link'.
+        if self._allow_harmful_protocols is True:
+            return escape_text(url)
+        _url = url.lower().lstrip()
+        if (
+            _url.startswith(self.SAFE_PROTOCOLS)
+            or _url.startswith(self.GOOD_DATA_PROTOCOLS)
+            or _url.startswith(("/", "#", "?"))
+            or ":" not in _url.split("/", 1)[0]   # bare relative path
+        ):
+            return escape_text(url)
+        if self._allow_harmful_protocols and _url.startswith(tuple(self._allow_harmful_protocols)):
+            return escape_text(url)
+        return "#harmful-link"

The allow_harmful_protocols option is preserved, so callers who genuinely want to allow a custom scheme can still opt in. The lower().lstrip() also closes the leading-whitespace evasion sub-case (e.g., javascript: is already blocked by the current code via lower().startswith, but the same pattern needs to apply on the new allowlist branch). Add regression tests for each scheme listed in the PoC above asserting they resolve to #harmful-link.

Severity
6.1 (Medium)
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
Show details on source website
To clipboard 

{
  "affected": [
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "mistune"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "3.3.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-59929"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-184",
      "CWE-79"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-07-20T21:35:30Z",
    "nvd_published_at": "2026-07-08T17:17:28Z",
    "severity": "MODERATE"
  },
  "details": "## Summary\n\n**Type:** URL-scheme allowlist gap. The `safe_url` filter only blocks the four schemes `javascript:`, `vbscript:`, `file:`, `data:`. Several other schemes are accepted into rendered `\u003ca href=\"...\"\u003e` and `\u003cimg src=\"...\"\u003e` tags despite being known XSS vectors in legacy or chain-handling browsers. The same gap applies to direct links, reference links, and autolinks.\n**File:** `src/mistune/renderers/html.py`, line 11-23 (HARMFUL_PROTOCOLS list).\n**Root cause:** the HARMFUL_PROTOCOLS tuple is a hardcoded, opt-out denylist of four entries. Browsers historically supported (and some still partially support) several other schemes that either execute JavaScript directly (`livescript:`, `mocha:`) or wrap a `javascript:` payload (`feed:javascript:`, `view-source:javascript:`, `jar:javascript:`, `ms-its:javascript:`, `mk:@MSITStore:javascript:`). On user-agents that still recognise these schemes (older Firefox builds for `feed:`/`jar:`, all Internet Explorer / Edge Legacy for `ms-its:`/`mk:`/`res:`, niche chrome-style browsers, browser extensions that register custom protocol handlers), clicking a link rendered by mistune executes attacker-controlled JavaScript in the page\u0027s origin.\n\n## Affected Code\n\n**File:** `src/mistune/renderers/html.py`, lines 10-62.\n\n```python\nclass HTMLRenderer(BaseRenderer):\n    HARMFUL_PROTOCOLS: ClassVar[Tuple[str, ...]] = (\n        \"javascript:\",\n        \"vbscript:\",\n        \"file:\",\n        \"data:\",\n    )                                                         # \u003c-- BUG: incomplete denylist\n    GOOD_DATA_PROTOCOLS: ClassVar[Tuple[str, ...]] = (\n        \"data:image/gif;\",\n        \"data:image/png;\",\n        \"data:image/jpeg;\",\n        \"data:image/webp;\",\n    )\n\n    def safe_url(self, url: str) -\u003e str:\n        if self._allow_harmful_protocols is True:\n            return escape_text(url)\n        _url = url.lower()\n        if self._allow_harmful_protocols and _url.startswith(tuple(self._allow_harmful_protocols)):\n            return escape_text(url)\n        if _url.startswith(self.HARMFUL_PROTOCOLS) and not _url.startswith(self.GOOD_DATA_PROTOCOLS):\n            return \"#harmful-link\"\n        return escape_text(url)                               # \u003c-- BUG: any scheme not in HARMFUL_PROTOCOLS passes through\n```\n\n**Why it\u0027s wrong:** an opt-out denylist for URL schemes is the wrong shape. The set of schemes a user-agent might honour is unbounded (registered handlers, browser extensions, OS-level protocol registrations, custom intent handlers on Android, etc.), but the set of schemes a markdown renderer needs to allow is small (`http://`, `https://`, `mailto:`, optionally `tel:`, `ftp:`, fragment-only `#anchor`, and a few image-only `data:` types). Switching to an opt-in allowlist with a `safe_extra_protocols` knob for callers who need others would close every variant of this bug class permanently. The current code accepts every chained-scheme XSS vector for as long as the project remembers to keep the denylist current.\n\n## Exploit Chain\n\n1. Application accepts attacker-supplied markdown and renders it with mistune. The default `escape=True` prevents raw HTML, but link href/image src filtering is the only XSS defense for `[click](...)` and `![alt](...)` syntax.\n2. Attacker writes `[click here](feed:javascript:alert(document.cookie))`. mistune\u0027s `safe_url` checks `feed:javascript:alert(document.cookie)` against `HARMFUL_PROTOCOLS = (\u0027javascript:\u0027, \u0027vbscript:\u0027, \u0027file:\u0027, \u0027data:\u0027)` \u2014 none match. The href is escape_text\u0027d (HTML-entity escape) and emitted as `\u003ca href=\"feed:javascript:alert(document.cookie)\"\u003eclick here\u003c/a\u003e`.\n3. Victim using a Firefox build that still has the feed handler registered (extension, configuration, or LTS that retained the feed reader past the 64.0 removal \u2014 including some forks and ESR builds) clicks the link. Firefox\u0027s feed handler invokes the inner URL, which is `javascript:alert(...)`. JS executes in the page\u0027s origin. Victim\u0027s session cookie is exfiltrated.\n4. Same pattern for `livescript:alert(1)` (Netscape Communicator era, still recognised by some niche browsers / browser-emulator tools), `view-source:javascript:alert(1)` (Firefox, see CVE-2009-1938), `jar:javascript:alert(1)` (older Firefox), `ms-its:javascript:` (IE/Edge Legacy), `res:javascript:` (IE), `mk:@MSITStore:javascript:` (IE CHM viewer). Each user-agent that recognises one of these is exploitable; the user-agent population that recognises at least one is not negligible (corporate environments still running Edge Legacy compatibility mode, locked-down kiosk browsers, Android WebView in apps that register custom intent handlers, Linux distros with old Firefox ESR plus the `feed:` extension, etc.).\n\nThe same primitive applies to image src (`![](feed:javascript:...)` rendered as `\u003cimg src=\"feed:...\"\u003e`) \u2014 though most browsers don\u0027t fetch javascript: from img src, the same chained handler quirk applies on a few user-agents \u2014 and to reference links and autolinks (verified in the PoC below; the rendered HTML is identical regardless of which markdown link syntax is used).\n\n## Security Impact\n\n**Severity:** sec-moderate. Conditional XSS depending on user-agent. Modern Chrome / Edge Chromium / Safari ignore most of these schemes, but Firefox forks, Edge Legacy, in-app WebViews, browser extensions registering custom handlers, and corporate browser deployments are exposed. Defence-in-depth is the framing: a markdown renderer should not need to track which browsers still honour which legacy chained-scheme.\n**Attacker capability:** plant a link in any place the application renders user-supplied markdown. When clicked by a user-agent that honours the legacy scheme, the attacker\u0027s JavaScript runs in the page\u0027s origin (steal cookies, perform actions as the victim, etc.).\n**Preconditions:** application uses mistune to render attacker-influenced markdown. Default config. Victim user-agent is one of the affected populations. No specific mistune option is required.\n**Differential:** PoC-verified against mistune@3.2.1, default config. The following inputs all PASS the filter and reach the rendered HTML unchanged:\n\n```python\nimport mistune\nmd = mistune.create_markdown()\nfor url in [\n    \u0027feed:javascript:alert(1)\u0027,                  # Firefox feed handler chain\n    \u0027livescript:alert(1)\u0027,                       # Netscape, niche browsers\n    \u0027mocha:alert(1)\u0027,                            # Netscape, niche browsers\n    \u0027view-source:javascript:alert(1)\u0027,           # Firefox view-source chain (CVE-2009-1938 class)\n    \u0027jar:javascript:alert(1)\u0027,                   # Firefox jar: handler chain\n    \u0027ms-its:javascript:alert(1)\u0027,                # IE/Edge Legacy InfoTech Storage handler\n    \u0027mk:@MSITStore:javascript:alert(1)\u0027,         # IE CHM viewer chain\n    \u0027res:javascript:\u0027,                           # IE resource: handler\n]:\n    print(md(f\u0027[click]({url})\u0027).strip())\n\n# Output (each one passes the filter):\n#   \u003cp\u003e\u003ca href=\"feed:javascript:alert(1)\"\u003eclick\u003c/a\u003e\u003c/p\u003e\n#   \u003cp\u003e\u003ca href=\"livescript:alert(1)\"\u003eclick\u003c/a\u003e\u003c/p\u003e\n#   \u003cp\u003e\u003ca href=\"mocha:alert(1)\"\u003eclick\u003c/a\u003e\u003c/p\u003e\n#   \u003cp\u003e\u003ca href=\"view-source:javascript:alert(1)\"\u003eclick\u003c/a\u003e\u003c/p\u003e\n#   \u003cp\u003e\u003ca href=\"jar:javascript:alert(1)\"\u003eclick\u003c/a\u003e\u003c/p\u003e\n#   \u003cp\u003e\u003ca href=\"ms-its:javascript:alert(1)\"\u003eclick\u003c/a\u003e\u003c/p\u003e\n#   \u003cp\u003e\u003ca href=\"mk:@MSITStore:javascript:\"\u003eclick\u003c/a\u003e\u003c/p\u003e\n#   \u003cp\u003e\u003ca href=\"res:javascript:\"\u003eclick\u003c/a\u003e\u003c/p\u003e\n```\n\nFor comparison, the four schemes already in the denylist are correctly blocked: `javascript:`, `vbscript:`, `file:`, `data:text/html` all return `\u003ca href=\"#harmful-link\"\u003e`.\n\nThe same gap applies to reference links (`[click][ref]\\n\\n[ref]: feed:javascript:alert(1)` \u2192 `\u003ca href=\"feed:javascript:alert(1)\"\u003e`) and to autolinks (`\u003cfeed:javascript:alert(1)\u003e` \u2192 `\u003ca href=\"feed:javascript:alert(1)\"\u003e`).\n\n## Suggested Fix\n\nSwitch from denylist to allowlist. The set of schemes a markdown renderer needs to allow is small and well-known; the set of schemes that might trigger handler chains is unbounded.\n\n```diff\n--- a/src/mistune/renderers/html.py\n+++ b/src/mistune/renderers/html.py\n@@ -7,21 +7,28 @@ class HTMLRenderer(BaseRenderer):\n\n     _escape: bool\n     NAME: ClassVar[Literal[\"html\"]] = \"html\"\n-    HARMFUL_PROTOCOLS: ClassVar[Tuple[str, ...]] = (\n-        \"javascript:\",\n-        \"vbscript:\",\n-        \"file:\",\n-        \"data:\",\n-    )\n+    SAFE_PROTOCOLS: ClassVar[Tuple[str, ...]] = (\n+        \"http:\",\n+        \"https:\",\n+        \"mailto:\",\n+        \"tel:\",\n+        \"ftp:\",\n+        \"ftps:\",\n+        \"irc:\",\n+        \"ircs:\",\n+    )\n     GOOD_DATA_PROTOCOLS: ClassVar[Tuple[str, ...]] = (\n         \"data:image/gif;\",\n         \"data:image/png;\",\n         \"data:image/jpeg;\",\n         \"data:image/webp;\",\n     )\n\n@@ -49,15 +56,21 @@ class HTMLRenderer(BaseRenderer):\n     def safe_url(self, url: str) -\u003e str:\n-        if self._allow_harmful_protocols is True:\n-            return escape_text(url)\n-\n-        _url = url.lower()\n-        if self._allow_harmful_protocols and _url.startswith(tuple(self._allow_harmful_protocols)):\n-            return escape_text(url)\n-\n-        if _url.startswith(self.HARMFUL_PROTOCOLS) and not _url.startswith(self.GOOD_DATA_PROTOCOLS):\n-            return \"#harmful-link\"\n-        return escape_text(url)\n+        # Allow-list: only schemes in SAFE_PROTOCOLS, image-only data: URLs in\n+        # GOOD_DATA_PROTOCOLS, scheme-relative URLs (//host/path), absolute\n+        # paths (/path), and anchor-only references (#fragment) reach the\n+        # rendered output. Everything else is replaced with \u0027#harmful-link\u0027.\n+        if self._allow_harmful_protocols is True:\n+            return escape_text(url)\n+        _url = url.lower().lstrip()\n+        if (\n+            _url.startswith(self.SAFE_PROTOCOLS)\n+            or _url.startswith(self.GOOD_DATA_PROTOCOLS)\n+            or _url.startswith((\"/\", \"#\", \"?\"))\n+            or \":\" not in _url.split(\"/\", 1)[0]   # bare relative path\n+        ):\n+            return escape_text(url)\n+        if self._allow_harmful_protocols and _url.startswith(tuple(self._allow_harmful_protocols)):\n+            return escape_text(url)\n+        return \"#harmful-link\"\n```\n\nThe `allow_harmful_protocols` option is preserved, so callers who genuinely want to allow a custom scheme can still opt in. The `lower().lstrip()` also closes the leading-whitespace evasion sub-case (e.g., ` javascript:` is already blocked by the current code via `lower().startswith`, but the same pattern needs to apply on the new allowlist branch). Add regression tests for each scheme listed in the PoC above asserting they resolve to `#harmful-link`.",
  "id": "GHSA-qfrw-5rxm-mhh2",
  "modified": "2026-07-20T21:35:30Z",
  "published": "2026-07-20T21:35:30Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/lepture/mistune/security/advisories/GHSA-qfrw-5rxm-mhh2"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-59929"
    },
    {
      "type": "WEB",
      "url": "https://github.com/lepture/mistune/commit/c7101fcbb6e8790e8e39157c5ca2238fc6dd6cbc"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/lepture/mistune"
    },
    {
      "type": "WEB",
      "url": "https://github.com/lepture/mistune/releases/tag/v3.3.0"
    },
    {
      "type": "WEB",
      "url": "https://github.com/pypa/advisory-database/tree/main/vulns/mistune/PYSEC-2026-2217.yaml"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Mistune renderers/html.safe_url: HARMFUL_PROTOCOLS list misses legacy and chained schemes that historically chain to `javascript:` execution"
}

GHSA-QFRW-X46F-QV6R

Vulnerability from github – Published: 2024-11-19 18:31 – Updated: 2026-04-01 18:32
VLAI
Details

Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') vulnerability in Bamboo Mcr Bamboo Enquiries allows Stored XSS.This issue affects Bamboo Enquiries: from n/a through 1.9.3.

Severity
6.5 (Medium)
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:L
Show details on source website
To clipboard 

{
  "affected": [],
  "aliases": [
    "CVE-2024-51859"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-79"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2024-11-19T17:15:37Z",
    "severity": "MODERATE"
  },
  "details": "Improper Neutralization of Input During Web Page Generation (\u0027Cross-site Scripting\u0027) vulnerability in Bamboo Mcr Bamboo Enquiries allows Stored XSS.This issue affects Bamboo Enquiries: from n/a through 1.9.3.",
  "id": "GHSA-qfrw-x46f-qv6r",
  "modified": "2026-04-01T18:32:32Z",
  "published": "2024-11-19T18:31:03Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2024-51859"
    },
    {
      "type": "WEB",
      "url": "https://patchstack.com/database/Wordpress/Plugin/bamboo-enquiries/vulnerability/wordpress-bamboo-enquiries-plugin-1-9-3-stored-cross-site-scripting-xss-vulnerability?_s_id=cve"
    },
    {
      "type": "WEB",
      "url": "https://patchstack.com/database/vulnerability/bamboo-enquiries/wordpress-bamboo-enquiries-plugin-1-9-3-stored-cross-site-scripting-xss-vulnerability?_s_id=cve"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:L",
      "type": "CVSS_V3"
    }
  ]
}

GHSA-QFV6-M2PJ-VX4R

Vulnerability from github – Published: 2024-12-11 00:31 – Updated: 2024-12-11 00:31
VLAI
Details

Adobe Experience Manager versions 6.5.21 and earlier are affected by a DOM-based Cross-Site Scripting (XSS) vulnerability that could be exploited by an attacker to execute arbitrary code in the context of the victim's browser session. By manipulating a DOM element through a crafted URL or user input, the attacker can inject malicious scripts that run when the page is rendered. This type of attack requires user interaction, as the victim would need to access the manipulated URL or input the malicious data themselves.

Severity
5.4 (Medium)
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
Show details on source website
To clipboard 

{
  "affected": [],
  "aliases": [
    "CVE-2024-52840"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-79"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2024-12-10T22:15:19Z",
    "severity": "MODERATE"
  },
  "details": "Adobe Experience Manager versions 6.5.21 and earlier are affected by a DOM-based Cross-Site Scripting (XSS) vulnerability that could be exploited by an attacker to execute arbitrary code in the context of the victim\u0027s browser session. By manipulating a DOM element through a crafted URL or user input, the attacker can inject malicious scripts that run when the page is rendered. This type of attack requires user interaction, as the victim would need to access the manipulated URL or input the malicious data themselves.",
  "id": "GHSA-qfv6-m2pj-vx4r",
  "modified": "2024-12-11T00:31:27Z",
  "published": "2024-12-11T00:31:26Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2024-52840"
    },
    {
      "type": "WEB",
      "url": "https://helpx.adobe.com/security/products/experience-manager/apsb24-69.html"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N",
      "type": "CVSS_V3"
    }
  ]
}

GHSA-QFVQ-H39H-4M98

Vulnerability from github – Published: 2022-09-22 00:00 – Updated: 2022-09-25 00:00
VLAI
Details

Authenticated (subscriber+) Reflected Cross-Site Scripting (XSS) vulnerability in Totalsoft Event Calendar – Calendar plugin <= 1.4.6 at WordPress.

Severity
5.4 (Medium)
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
Show details on source website
To clipboard 

{
  "affected": [],
  "aliases": [
    "CVE-2022-36390"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-79"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2022-09-21T20:15:00Z",
    "severity": "MODERATE"
  },
  "details": "Authenticated (subscriber+) Reflected Cross-Site Scripting (XSS) vulnerability in Totalsoft Event Calendar \u2013 Calendar plugin \u003c= 1.4.6 at WordPress.",
  "id": "GHSA-qfvq-h39h-4m98",
  "modified": "2022-09-25T00:00:28Z",
  "published": "2022-09-22T00:00:22Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2022-36390"
    },
    {
      "type": "WEB",
      "url": "https://patchstack.com/database/vulnerability/calendar-event/wordpress-event-calendar-calendar-plugin-1-4-6-authenticated-reflected-cross-site-scripting-xss-vulnerability"
    },
    {
      "type": "WEB",
      "url": "https://wordpress.org/plugins/calendar-event/#developers"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N",
      "type": "CVSS_V3"
    }
  ]
}

GHSA-QFW5-7XHP-MHJ4

Vulnerability from github – Published: 2025-09-22 21:30 – Updated: 2026-04-01 18:36
VLAI
Details

Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') vulnerability in snapwidget SnapWidget Social Photo Feed Widget allows DOM-Based XSS. This issue affects SnapWidget Social Photo Feed Widget: from n/a through 1.1.0.

Severity
6.5 (Medium)
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:L
Show details on source website
To clipboard 

{
  "affected": [],
  "aliases": [
    "CVE-2025-58241"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-79"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2025-09-22T19:16:09Z",
    "severity": "MODERATE"
  },
  "details": "Improper Neutralization of Input During Web Page Generation (\u0027Cross-site Scripting\u0027) vulnerability in snapwidget SnapWidget Social Photo Feed Widget allows DOM-Based XSS. This issue affects SnapWidget Social Photo Feed Widget: from n/a through 1.1.0.",
  "id": "GHSA-qfw5-7xhp-mhj4",
  "modified": "2026-04-01T18:36:15Z",
  "published": "2025-09-22T21:30:26Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2025-58241"
    },
    {
      "type": "WEB",
      "url": "https://patchstack.com/database/wordpress/plugin/snapwidget-wp-instagram-widget/vulnerability/wordpress-snapwidget-social-photo-feed-widget-plugin-1-1-0-cross-site-scripting-xss-vulnerability-2?_s_id=cve"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:L",
      "type": "CVSS_V3"
    }
  ]
}

GHSA-QFW5-995H-4GJP

Vulnerability from github – Published: 2024-08-25 03:30 – Updated: 2024-08-25 03:30
VLAI
Details

A vulnerability was found in SourceCodester Daily Calories Monitoring Tool 1.0. It has been declared as problematic. This vulnerability affects unknown code of the file /endpoint/delete-calorie.php. The manipulation of the argument calorie leads to cross site scripting. The attack can be initiated remotely. The exploit has been disclosed to the public and may be used.

Severity
3.5 (Low)
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:L/A:N
5.3 (Medium)
CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N
Show details on source website
To clipboard 

{
  "affected": [],
  "aliases": [
    "CVE-2024-8142"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-79"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2024-08-25T03:15:03Z",
    "severity": "MODERATE"
  },
  "details": "A vulnerability was found in SourceCodester Daily Calories Monitoring Tool 1.0. It has been declared as problematic. This vulnerability affects unknown code of the file /endpoint/delete-calorie.php. The manipulation of the argument calorie leads to cross site scripting. The attack can be initiated remotely. The exploit has been disclosed to the public and may be used.",
  "id": "GHSA-qfw5-995h-4gjp",
  "modified": "2024-08-25T03:30:32Z",
  "published": "2024-08-25T03:30:32Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2024-8142"
    },
    {
      "type": "WEB",
      "url": "https://github.com/jadu101/CVE/blob/main/SourceCodester_Daily_Calories_Monitoring_Tool_delete_calorie_XSS.md"
    },
    {
      "type": "WEB",
      "url": "https://vuldb.com/?ctiid.275722"
    },
    {
      "type": "WEB",
      "url": "https://vuldb.com/?id.275722"
    },
    {
      "type": "WEB",
      "url": "https://vuldb.com/?submit.396899"
    },
    {
      "type": "WEB",
      "url": "https://www.sourcecodester.com"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:L/A:N",
      "type": "CVSS_V3"
    },
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
      "type": "CVSS_V4"
    }
  ]
}

GHSA-QFW7-PFXX-H9Q2

Vulnerability from github – Published: 2023-08-14 18:32 – Updated: 2023-08-23 20:07
VLAI
Summary
OpenNMS vulnerable to Cross-site Scripting
Details

Multiple stored XSS were found on different JSP files with unsanitized parameters in OpenMNS Horizon 31.0.8 and versions earlier than 32.0.2 on multiple platforms that allow an attacker to store on database and then load on JSPs or Angular templates. The solution is to upgrade to Meridian 2023.1.6, 2022.1.19, 2021.1.30, 2020.1.38 or Horizon 32.0.2 or newer. Meridian and Horizon installation instructions state that they are intended for installation within an organization's private networks and should not be directly accessible from the Internet. OpenNMS thanks Jordi Miralles Comins for reporting this issue.

Severity
6.7 (Medium)
CVSS:3.1/AV:A/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:N
Show details on source website
To clipboard 

{
  "affected": [
    {
      "package": {
        "ecosystem": "Maven",
        "name": "org.opennms:opennms-webapp"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "31.0.8"
            },
            {
              "fixed": "32.0.2"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2023-40311"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-79"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2023-08-14T21:12:09Z",
    "nvd_published_at": "2023-08-14T18:15:11Z",
    "severity": "MODERATE"
  },
  "details": "Multiple stored XSS were found on different JSP files with unsanitized parameters in OpenMNS Horizon 31.0.8 and versions earlier than 32.0.2 on multiple platforms that allow an attacker to store on database and then load on JSPs or Angular templates. The solution is to upgrade to Meridian 2023.1.6, 2022.1.19, 2021.1.30, 2020.1.38 or Horizon 32.0.2 or newer. Meridian and Horizon installation instructions state that they are intended for installation within an organization\u0027s private networks and should not be directly accessible from the Internet. OpenNMS thanks\u00a0Jordi Miralles Comins for reporting this issue.\n",
  "id": "GHSA-qfw7-pfxx-h9q2",
  "modified": "2023-08-23T20:07:41Z",
  "published": "2023-08-14T18:32:59Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2023-40311"
    },
    {
      "type": "WEB",
      "url": "https://github.com/OpenNMS/opennms/pull/6365"
    },
    {
      "type": "WEB",
      "url": "https://github.com/OpenNMS/opennms/pull/6366"
    },
    {
      "type": "WEB",
      "url": "https://github.com/OpenNMS/opennms/commit/6ccc5de1a23d440560e0f09dfd94f8392c21e70d"
    },
    {
      "type": "WEB",
      "url": "https://github.com/OpenNMS/opennms/commit/c67d1cae2fa1fb806c9d422f6e6fbf4ebfde6b60"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/OpenNMS/opennms"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:A/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "OpenNMS vulnerable to Cross-site Scripting"
}

GHSA-QFW9-G7JH-72P3

Vulnerability from github – Published: 2023-10-18 15:30 – Updated: 2024-04-04 08:46
VLAI
Details

Auth. (admin+) Stored Cross-Site Scripting (XSS) vulnerability in Kardi Order auto complete for WooCommerce plugin <= 1.2.0 versions.

Severity
5.9 (Medium)
CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/A:L
Show details on source website
To clipboard 

{
  "affected": [],
  "aliases": [
    "CVE-2023-45072"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-79"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2023-10-18T13:15:09Z",
    "severity": "MODERATE"
  },
  "details": "Auth. (admin+) Stored Cross-Site Scripting (XSS) vulnerability in Kardi Order auto complete for WooCommerce plugin \u003c=\u00a01.2.0 versions.",
  "id": "GHSA-qfw9-g7jh-72p3",
  "modified": "2024-04-04T08:46:13Z",
  "published": "2023-10-18T15:30:24Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2023-45072"
    },
    {
      "type": "WEB",
      "url": "https://patchstack.com/database/vulnerability/order-auto-complete-for-woocommerce/wordpress-order-auto-complete-for-woocommerce-plugin-1-2-0-cross-site-scripting-xss-vulnerability?_s_id=cve"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/A:L",
      "type": "CVSS_V3"
    }
  ]
}

GHSA-QFWF-5HGC-R5J2

Vulnerability from github – Published: 2022-10-21 19:01 – Updated: 2025-05-08 15:30
VLAI
Details

PHPGurukul Hospital Management System In PHP V 4.0 is vulnerable to Cross Site Scripting (XSS) via add-patient.php.

Severity
5.4 (Medium)
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
Show details on source website
To clipboard 

{
  "affected": [],
  "aliases": [
    "CVE-2022-42205"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-79"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2022-10-21T13:15:00Z",
    "severity": "MODERATE"
  },
  "details": "PHPGurukul Hospital Management System In PHP V 4.0 is vulnerable to Cross Site Scripting (XSS) via add-patient.php.",
  "id": "GHSA-qfwf-5hgc-r5j2",
  "modified": "2025-05-08T15:30:33Z",
  "published": "2022-10-21T19:01:16Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2022-42205"
    },
    {
      "type": "WEB",
      "url": "https://sisl.lab.uic.edu/projects/chess/cross-site-scripting-in-hms2"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N",
      "type": "CVSS_V3"
    }
  ]
}

GHSA-QFWH-JRHV-2RG3

Vulnerability from github – Published: 2024-06-08 15:31 – Updated: 2026-04-01 18:31
VLAI
Details

Improper Neutralization of Input During Web Page Generation (XSS or 'Cross-site Scripting') vulnerability in YITH YITH WooCommerce Tab Manager allows Stored XSS.This issue affects YITH WooCommerce Tab Manager: from n/a through 1.35.0.

Severity
5.9 (Medium)
CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/A:L
Show details on source website
To clipboard 

{
  "affected": [],
  "aliases": [
    "CVE-2024-35698"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-79"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2024-06-08T15:15:53Z",
    "severity": "MODERATE"
  },
  "details": "Improper Neutralization of Input During Web Page Generation (XSS or \u0027Cross-site Scripting\u0027) vulnerability in YITH YITH WooCommerce Tab Manager allows Stored XSS.This issue affects YITH WooCommerce Tab Manager: from n/a through 1.35.0.",
  "id": "GHSA-qfwh-jrhv-2rg3",
  "modified": "2026-04-01T18:31:48Z",
  "published": "2024-06-08T15:31:19Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2024-35698"
    },
    {
      "type": "WEB",
      "url": "https://patchstack.com/database/Wordpress/Plugin/yith-woocommerce-tab-manager/vulnerability/wordpress-yith-woocommerce-tab-manager-plugin-1-35-0-cross-site-scripting-xss-vulnerability?_s_id=cve"
    },
    {
      "type": "WEB",
      "url": "https://patchstack.com/database/vulnerability/yith-woocommerce-tab-manager/wordpress-yith-woocommerce-tab-manager-plugin-1-35-0-cross-site-scripting-xss-vulnerability?_s_id=cve"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:C/C:L/I:L/A:L",
      "type": "CVSS_V3"
    }
  ]
}
Mitigation MIT-4
Architecture and Design

Strategy: Libraries or Frameworks

  • Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid [REF-1482].
  • Examples of libraries and frameworks that make it easier to generate properly encoded output include Microsoft's Anti-XSS library, the OWASP ESAPI Encoding module, and Apache Wicket.
Mitigation
Implementation Architecture and Design
  • Understand the context in which your data will be used and the encoding that will be expected. This is especially important when transmitting data between different components, or when generating outputs that can contain multiple encodings at the same time, such as web pages or multi-part mail messages. Study all expected communication protocols and data representations to determine the required encoding strategies.
  • For any data that will be output to another web page, especially any data that was received from external inputs, use the appropriate encoding on all non-alphanumeric characters.
  • Parts of the same output document may require different encodings, which will vary depending on whether the output is in the:
  • etc. Note that HTML Entity Encoding is only appropriate for the HTML body.
  • Consult the XSS Prevention Cheat Sheet [REF-724] for more details on the types of encoding and escaping that are needed.
  • HTML body
  • Element attributes (such as src="XYZ")
  • URIs
  • JavaScript sections
  • Cascading Style Sheets and style property
Mitigation MIT-6
Architecture and Design Implementation

Strategy: Attack Surface Reduction

Understand all the potential areas where untrusted inputs can enter your software: parameters or arguments, cookies, anything read from the network, environment variables, reverse DNS lookups, query results, request headers, URL components, e-mail, files, filenames, databases, and any external systems that provide data to the application. Remember that such inputs may be obtained indirectly through API calls.

Mitigation MIT-15
Architecture and Design

For any security checks that are performed on the client side, ensure that these checks are duplicated on the server side, in order to avoid CWE-602. Attackers can bypass the client-side checks by modifying values after the checks have been performed, or by changing the client to remove the client-side checks entirely. Then, these modified values would be submitted to the server.

Mitigation MIT-27
Architecture and Design

Strategy: Parameterization

If available, use structured mechanisms that automatically enforce the separation between data and code. These mechanisms may be able to provide the relevant quoting, encoding, and validation automatically, instead of relying on the developer to provide this capability at every point where output is generated.

Mitigation MIT-30.1
Implementation

Strategy: Output Encoding

  • Use and specify an output encoding that can be handled by the downstream component that is reading the output. Common encodings include ISO-8859-1, UTF-7, and UTF-8. When an encoding is not specified, a downstream component may choose a different encoding, either by assuming a default encoding or automatically inferring which encoding is being used, which can be erroneous. When the encodings are inconsistent, the downstream component might treat some character or byte sequences as special, even if they are not special in the original encoding. Attackers might then be able to exploit this discrepancy and conduct injection attacks; they even might be able to bypass protection mechanisms that assume the original encoding is also being used by the downstream component.
  • The problem of inconsistent output encodings often arises in web pages. If an encoding is not specified in an HTTP header, web browsers often guess about which encoding is being used. This can open up the browser to subtle XSS attacks.
Mitigation MIT-43
Implementation

With Struts, write all data from form beans with the bean's filter attribute set to true.

Mitigation MIT-31
Implementation

Strategy: Attack Surface Reduction

To help mitigate XSS attacks against the user's session cookie, set the session cookie to be HttpOnly. In browsers that support the HttpOnly feature (such as more recent versions of Internet Explorer and Firefox), this attribute can prevent the user's session cookie from being accessible to malicious client-side scripts that use document.cookie. This is not a complete solution, since HttpOnly is not supported by all browsers. More importantly, XmlHttpRequest and other powerful browser technologies provide read access to HTTP headers, including the Set-Cookie header in which the HttpOnly flag is set.

Mitigation MIT-5
Implementation

Strategy: Input Validation

  • Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.
  • When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, "boat" may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as "red" or "blue."
  • Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code's environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.
  • When dynamically constructing web pages, use stringent allowlists that limit the character set based on the expected value of the parameter in the request. All input should be validated and cleansed, not just parameters that the user is supposed to specify, but all data in the request, including hidden fields, cookies, headers, the URL itself, and so forth. A common mistake that leads to continuing XSS vulnerabilities is to validate only fields that are expected to be redisplayed by the site. It is common to see data from the request that is reflected by the application server or the application that the development team did not anticipate. Also, a field that is not currently reflected may be used by a future developer. Therefore, validating ALL parts of the HTTP request is recommended.
  • Note that proper output encoding, escaping, and quoting is the most effective solution for preventing XSS, although input validation may provide some defense-in-depth. This is because it effectively limits what will appear in output. Input validation will not always prevent XSS, especially if you are required to support free-form text fields that could contain arbitrary characters. For example, in a chat application, the heart emoticon ("<3") would likely pass the validation step, since it is commonly used. However, it cannot be directly inserted into the web page because it contains the "<" character, which would need to be escaped or otherwise handled. In this case, stripping the "<" might reduce the risk of XSS, but it would produce incorrect behavior because the emoticon would not be recorded. This might seem to be a minor inconvenience, but it would be more important in a mathematical forum that wants to represent inequalities.
  • Even if you make a mistake in your validation (such as forgetting one out of 100 input fields), appropriate encoding is still likely to protect you from injection-based attacks. As long as it is not done in isolation, input validation is still a useful technique, since it may significantly reduce your attack surface, allow you to detect some attacks, and provide other security benefits that proper encoding does not address.
  • Ensure that you perform input validation at well-defined interfaces within the application. This will help protect the application even if a component is reused or moved elsewhere.
Mitigation MIT-21
Architecture and Design

Strategy: Enforcement by Conversion

When the set of acceptable objects, such as filenames or URLs, is limited or known, create a mapping from a set of fixed input values (such as numeric IDs) to the actual filenames or URLs, and reject all other inputs.

Mitigation MIT-29
Operation

Strategy: Firewall

Use an application firewall that can detect attacks against this weakness. It can be beneficial in cases in which the code cannot be fixed (because it is controlled by a third party), as an emergency prevention measure while more comprehensive software assurance measures are applied, or to provide defense in depth [REF-1481].

Mitigation MIT-16
Operation Implementation

Strategy: Environment Hardening

When using PHP, configure the application so that it does not use register_globals. During implementation, develop the application so that it does not rely on this feature, but be wary of implementing a register_globals emulation that is subject to weaknesses such as CWE-95, CWE-621, and similar issues.

CAPEC-209: XSS Using MIME Type Mismatch

An adversary creates a file with scripting content but where the specified MIME type of the file is such that scripting is not expected. The adversary tricks the victim into accessing a URL that responds with the script file. Some browsers will detect that the specified MIME type of the file does not match the actual type of its content and will automatically switch to using an interpreter for the real content type. If the browser does not invoke script filters before doing this, the adversary's script may run on the target unsanitized, possibly revealing the victim's cookies or executing arbitrary script in their browser.

CAPEC-588: DOM-Based XSS

This type of attack is a form of Cross-Site Scripting (XSS) where a malicious script is inserted into the client-side HTML being parsed by a web browser. Content served by a vulnerable web application includes script code used to manipulate the Document Object Model (DOM). This script code either does not properly validate input, or does not perform proper output encoding, thus creating an opportunity for an adversary to inject a malicious script launch a XSS attack. A key distinction between other XSS attacks and DOM-based attacks is that in other XSS attacks, the malicious script runs when the vulnerable web page is initially loaded, while a DOM-based attack executes sometime after the page loads. Another distinction of DOM-based attacks is that in some cases, the malicious script is never sent to the vulnerable web server at all. An attack like this is guaranteed to bypass any server-side filtering attempts to protect users.

CAPEC-591: Reflected XSS

This type of attack is a form of Cross-Site Scripting (XSS) where a malicious script is "reflected" off a vulnerable web application and then executed by a victim's browser. The process starts with an adversary delivering a malicious script to a victim and convincing the victim to send the script to the vulnerable web application.

CAPEC-592: Stored XSS

An adversary utilizes a form of Cross-site Scripting (XSS) where a malicious script is persistently "stored" within the data storage of a vulnerable web application as valid input.

CAPEC-63: Cross-Site Scripting (XSS)

An adversary embeds malicious scripts in content that will be served to web browsers. The goal of the attack is for the target software, the client-side browser, to execute the script with the users' privilege level. An attack of this type exploits a programs' vulnerabilities that are brought on by allowing remote hosts to execute code and scripts. Web browsers, for example, have some simple security controls in place, but if a remote attacker is allowed to execute scripts (through injecting them in to user-generated content like bulletin boards) then these controls may be bypassed. Further, these attacks are very difficult for an end user to detect.

CAPEC-85: AJAX Footprinting

This attack utilizes the frequent client-server roundtrips in Ajax conversation to scan a system. While Ajax does not open up new vulnerabilities per se, it does optimize them from an attacker point of view. A common first step for an attacker is to footprint the target environment to understand what attacks will work. Since footprinting relies on enumeration, the conversational pattern of rapid, multiple requests and responses that are typical in Ajax applications enable an attacker to look for many vulnerabilities, well-known ports, network locations and so on. The knowledge gained through Ajax fingerprinting can be used to support other attacks, such as XSS.

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