CWE-79
AllowedImproper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Abstraction: Base · Status: Stable
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.
68971 vulnerabilities reference this CWE, most recent first.
GHSA-932H-RJ9Q-CG85
Vulnerability from github – Published: 2025-02-24 00:30 – Updated: 2025-02-24 00:30A vulnerability was found in SourceCodester Best Church Management Software 1.0. It has been classified as problematic. Affected is an unknown function of the file /admin/redirect.php. The manipulation of the argument a leads to cross site scripting. It is possible to launch the attack remotely. The exploit has been disclosed to the public and may be used. The vendor was contacted early about this disclosure but did not respond in any way.
{
"affected": [],
"aliases": [
"CVE-2025-1597"
],
"database_specific": {
"cwe_ids": [
"CWE-79"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2025-02-23T23:15:10Z",
"severity": "MODERATE"
},
"details": "A vulnerability was found in SourceCodester Best Church Management Software 1.0. It has been classified as problematic. Affected is an unknown function of the file /admin/redirect.php. The manipulation of the argument a leads to cross site scripting. It is possible to launch the attack remotely. The exploit has been disclosed to the public and may be used. The vendor was contacted early about this disclosure but did not respond in any way.",
"id": "GHSA-932h-rj9q-cg85",
"modified": "2025-02-24T00:30:55Z",
"published": "2025-02-24T00:30:55Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2025-1597"
},
{
"type": "WEB",
"url": "https://github.com/xiahao90/CVEproject/blob/main/xiahao.webray.com.cn/best-church-management-software-xss.md"
},
{
"type": "WEB",
"url": "https://vuldb.com/?ctiid.296592"
},
{
"type": "WEB",
"url": "https://vuldb.com/?id.296592"
},
{
"type": "WEB",
"url": "https://vuldb.com/?submit.497883"
},
{
"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:P/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-933C-WXWW-RPJP
Vulnerability from github – Published: 2022-05-17 01:48 – Updated: 2022-05-17 01:48Cross-site scripting (XSS) vulnerability in Joomla! 2.5.0 and 2.5.1 allows remote attackers to inject arbitrary web script or HTML via unspecified vectors.
{
"affected": [],
"aliases": [
"CVE-2012-1117"
],
"database_specific": {
"cwe_ids": [
"CWE-79"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2012-09-26T00:55:00Z",
"severity": "MODERATE"
},
"details": "Cross-site scripting (XSS) vulnerability in Joomla! 2.5.0 and 2.5.1 allows remote attackers to inject arbitrary web script or HTML via unspecified vectors.",
"id": "GHSA-933c-wxww-rpjp",
"modified": "2022-05-17T01:48:48Z",
"published": "2022-05-17T01:48:48Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2012-1117"
},
{
"type": "WEB",
"url": "https://exchange.xforce.ibmcloud.com/vulnerabilities/73700"
},
{
"type": "WEB",
"url": "http://developer.joomla.org/security/news/392-20120302-core-xss-vulnerability.html"
},
{
"type": "WEB",
"url": "http://secunia.com/advisories/48005"
},
{
"type": "WEB",
"url": "http://www.openwall.com/lists/oss-security/2012/03/06/12"
},
{
"type": "WEB",
"url": "http://www.openwall.com/lists/oss-security/2012/03/06/5"
},
{
"type": "WEB",
"url": "http://www.osvdb.org/79836"
},
{
"type": "WEB",
"url": "http://www.securityfocus.com/bid/52314"
}
],
"schema_version": "1.4.0",
"severity": []
}
GHSA-933R-WHWG-5P39
Vulnerability from github – Published: 2022-05-24 19:16 – Updated: 2022-05-24 19:16IBM Sterling Order Management 9.4, 9.5, and 10.0 is vulnerable to cross-site scripting. This vulnerability allows users to embed arbitrary JavaScript code in the Web UI thus altering the intended functionality potentially leading to credentials disclosure within a trusted session. IBM X-Force ID: 199179.
{
"affected": [],
"aliases": [
"CVE-2021-20554"
],
"database_specific": {
"cwe_ids": [
"CWE-79"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2021-09-30T17:15:00Z",
"severity": "MODERATE"
},
"details": "IBM Sterling Order Management 9.4, 9.5, and 10.0 is vulnerable to cross-site scripting. This vulnerability allows users to embed arbitrary JavaScript code in the Web UI thus altering the intended functionality potentially leading to credentials disclosure within a trusted session. IBM X-Force ID: 199179.",
"id": "GHSA-933r-whwg-5p39",
"modified": "2022-05-24T19:16:12Z",
"published": "2022-05-24T19:16:12Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2021-20554"
},
{
"type": "WEB",
"url": "https://exchange.xforce.ibmcloud.com/vulnerabilities/199179"
},
{
"type": "WEB",
"url": "https://www.ibm.com/support/pages/node/6493881"
}
],
"schema_version": "1.4.0",
"severity": []
}
GHSA-934V-V23C-9736
Vulnerability from github – Published: 2024-11-09 12:30 – Updated: 2026-04-01 18:32Improper Neutralization of Input During Web Page Generation (XSS or 'Cross-site Scripting') vulnerability in Nightshift Creative PropertyShift allows Reflected XSS.This issue affects PropertyShift: from n/a through 1.0.0.
{
"affected": [],
"aliases": [
"CVE-2024-51762"
],
"database_specific": {
"cwe_ids": [
"CWE-79"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2024-11-09T10:15:06Z",
"severity": "HIGH"
},
"details": "Improper Neutralization of Input During Web Page Generation (XSS or \u0027Cross-site Scripting\u0027) vulnerability in Nightshift Creative PropertyShift allows Reflected XSS.This issue affects PropertyShift: from n/a through 1.0.0.",
"id": "GHSA-934v-v23c-9736",
"modified": "2026-04-01T18:32:18Z",
"published": "2024-11-09T12:30:46Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2024-51762"
},
{
"type": "WEB",
"url": "https://patchstack.com/database/Wordpress/Plugin/propertyshift/vulnerability/wordpress-propertyshift-plugin-1-0-0-reflected-cross-site-scripting-xss-vulnerability?_s_id=cve"
},
{
"type": "WEB",
"url": "https://patchstack.com/database/vulnerability/propertyshift/wordpress-propertyshift-plugin-1-0-0-reflected-cross-site-scripting-xss-vulnerability?_s_id=cve"
}
],
"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:L",
"type": "CVSS_V3"
}
]
}
GHSA-934W-87QH-QR26
Vulnerability from github – Published: 2026-06-16 13:49 – Updated: 2026-08-14 18:45Summary
<NuxtLink> did not validate the URL scheme of values bound to its to or href props before rendering them into the href attribute of the underlying <a> element. When an application binds attacker-controlled input (a query parameter, a CMS field, a user-supplied profile URL) to <NuxtLink :to> or :href, the attacker can supply a javascript: or vbscript: URL that is reflected verbatim into the rendered markup. Clicking the link executes the supplied script in the origin of the Nuxt application, resulting in reflected DOM-based cross-site scripting. A data:text/html,... payload reflected through the same sink does not execute in the application's origin but enables a same-tab phishing surface anchored to a legitimate application link.
The same value was exposed to consumers of the component's custom slot via the href and route.href props, so applications that re-bind those values to their own anchors were affected identically.
Unlike the previously reported navigateTo issue (CVE-2024-34343), the sink here is the rendered anchor itself; the existing isScriptProtocol checks in navigateTo and reloadNuxtApp are not on the code path. The onClick handler intentionally returns early for external links so the browser's native protocol-based navigation runs.
Affected component
- File:
packages/nuxt/src/app/components/nuxt-link.ts - Sink:
h('a', { href: href.value, ... })in the default render, plus thehref/route.hrefprops passed to thecustomslot. - Broken check: external auto-detection treated any
hasProtocol(path, { acceptRelative: true })value as an "external link", then rendered the value directly as<a href>without rejecting script-capable protocols. There was no equivalent of thenavigateToisScriptProtocol(protocol)gate in this path.
Impact
Any Nuxt application that binds user-controlled values to <NuxtLink :to> / :href was vulnerable. Common shapes: profile-link rendering (<NuxtLink :to="user.website">), "share this" / "open in new tab" handlers that pass through a query parameter, CMS-driven landing pages that render <NuxtLink :to="cms.cta.url">, and marketplace listings that show seller-supplied links.
For javascript: / vbscript: the primitive is reflected XSS in the application's first-party origin (session theft for non-HttpOnly cookies, CSRF token theft, account takeover via DOM rewriting, credential harvesting via fake login overlays). For data:text/html,... the attacker gets a same-tab phishing surface anchored to a legitimate application link.
Patches
Fixed in nuxt@4.4.7 (commit 0103ce06) and backported to nuxt@3.21.7 (commit 53284043). The fix sanitises the resolved external href before it is passed to <a> or the custom slot: control characters and whitespace are stripped, leading view-source: prefixes are unwrapped, and any remaining script-capable scheme (per isScriptProtocol) causes the href to be replaced with an empty string.
Workarounds
Until you can upgrade, validate URLs at the source before binding them to <NuxtLink :to> / :href. For example, only accept paths that start with / (and not //), or run user-supplied URLs through new URL(value) and reject anything whose protocol is not in an allow-list (typically http: and https:).
{
"affected": [
{
"package": {
"ecosystem": "npm",
"name": "nuxt"
},
"ranges": [
{
"events": [
{
"introduced": "4.0.0"
},
{
"fixed": "4.4.7"
}
],
"type": "ECOSYSTEM"
}
]
},
{
"package": {
"ecosystem": "npm",
"name": "nuxt"
},
"ranges": [
{
"events": [
{
"introduced": "3.0.0"
},
{
"fixed": "3.21.7"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2026-53722"
],
"database_specific": {
"cwe_ids": [
"CWE-79",
"CWE-83"
],
"github_reviewed": true,
"github_reviewed_at": "2026-06-16T13:49:36Z",
"nvd_published_at": "2026-06-12T15:16:31Z",
"severity": "MODERATE"
},
"details": "### Summary\n\n`\u003cNuxtLink\u003e` did not validate the URL scheme of values bound to its `to` or `href` props before rendering them into the `href` attribute of the underlying `\u003ca\u003e` element. When an application binds attacker-controlled input (a query parameter, a CMS field, a user-supplied profile URL) to `\u003cNuxtLink :to\u003e` or `:href`, the attacker can supply a `javascript:` or `vbscript:` URL that is reflected verbatim into the rendered markup. Clicking the link executes the supplied script in the origin of the Nuxt application, resulting in reflected DOM-based cross-site scripting. A `data:text/html,...` payload reflected through the same sink does not execute in the application\u0027s origin but enables a same-tab phishing surface anchored to a legitimate application link.\n\nThe same value was exposed to consumers of the component\u0027s `custom` slot via the `href` and `route.href` props, so applications that re-bind those values to their own anchors were affected identically.\n\nUnlike the previously reported `navigateTo` issue (CVE-2024-34343), the sink here is the rendered anchor itself; the existing `isScriptProtocol` checks in `navigateTo` and `reloadNuxtApp` are not on the code path. The `onClick` handler intentionally returns early for external links so the browser\u0027s native protocol-based navigation runs.\n\n### Affected component\n\n- File: `packages/nuxt/src/app/components/nuxt-link.ts`\n- Sink: `h(\u0027a\u0027, { href: href.value, ... })` in the default render, plus the `href` / `route.href` props passed to the `custom` slot.\n- Broken check: external auto-detection treated any `hasProtocol(path, { acceptRelative: true })` value as an \"external link\", then rendered the value directly as `\u003ca href\u003e` without rejecting script-capable protocols. There was no equivalent of the `navigateTo` `isScriptProtocol(protocol)` gate in this path.\n\n### Impact\n\nAny Nuxt application that binds user-controlled values to `\u003cNuxtLink :to\u003e` / `:href` was vulnerable. Common shapes: profile-link rendering (`\u003cNuxtLink :to=\"user.website\"\u003e`), \"share this\" / \"open in new tab\" handlers that pass through a query parameter, CMS-driven landing pages that render `\u003cNuxtLink :to=\"cms.cta.url\"\u003e`, and marketplace listings that show seller-supplied links.\n\nFor `javascript:` / `vbscript:` the primitive is reflected XSS in the application\u0027s first-party origin (session theft for non-`HttpOnly` cookies, CSRF token theft, account takeover via DOM rewriting, credential harvesting via fake login overlays). For `data:text/html,...` the attacker gets a same-tab phishing surface anchored to a legitimate application link.\n\n### Patches\n\nFixed in `nuxt@4.4.7` (commit [`0103ce06`](https://github.com/nuxt/nuxt/commit/0103ce06fbbbdfa079a7f020ef8ce00121eac4a3)) and backported to `nuxt@3.21.7` (commit [`53284043`](https://github.com/nuxt/nuxt/commit/53284043dc21210a25d629d1cec67d3ae557ffd0)). The fix sanitises the resolved external `href` before it is passed to `\u003ca\u003e` or the `custom` slot: control characters and whitespace are stripped, leading `view-source:` prefixes are unwrapped, and any remaining script-capable scheme (per `isScriptProtocol`) causes the `href` to be replaced with an empty string.\n\n### Workarounds\n\nUntil you can upgrade, validate URLs at the source before binding them to `\u003cNuxtLink :to\u003e` / `:href`. For example, only accept paths that start with `/` (and not `//`), or run user-supplied URLs through `new URL(value)` and reject anything whose `protocol` is not in an allow-list (typically `http:` and `https:`).",
"id": "GHSA-934w-87qh-qr26",
"modified": "2026-08-14T18:45:56Z",
"published": "2026-06-16T13:49:36Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/nuxt/nuxt/security/advisories/GHSA-934w-87qh-qr26"
},
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-53722"
},
{
"type": "WEB",
"url": "https://github.com/nuxt/nuxt/commit/0103ce06fbbbdfa079a7f020ef8ce00121eac4a3"
},
{
"type": "WEB",
"url": "https://github.com/nuxt/nuxt/commit/53284043dc21210a25d629d1cec67d3ae557ffd0"
},
{
"type": "PACKAGE",
"url": "https://github.com/nuxt/nuxt"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N",
"type": "CVSS_V4"
}
],
"summary": "Nuxt: Reflected XSS in `\u003cNuxtLink\u003e` via unsanitised `javascript:` or `data:` URL"
}
GHSA-934W-8HRJ-JF38
Vulnerability from github – Published: 2024-03-27 06:30 – Updated: 2026-04-28 21:34Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') vulnerability in ThemeFusion Fusion Builder allows Reflected XSS.This issue affects Fusion Builder: from n/a through 3.11.1.
{
"affected": [],
"aliases": [
"CVE-2023-39306"
],
"database_specific": {
"cwe_ids": [
"CWE-79"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2024-03-27T06:15:09Z",
"severity": "HIGH"
},
"details": "Improper Neutralization of Input During Web Page Generation (\u0027Cross-site Scripting\u0027) vulnerability in ThemeFusion Fusion Builder allows Reflected XSS.This issue affects Fusion Builder: from n/a through 3.11.1.",
"id": "GHSA-934w-8hrj-jf38",
"modified": "2026-04-28T21:34:17Z",
"published": "2024-03-27T06:30:32Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2023-39306"
},
{
"type": "WEB",
"url": "https://patchstack.com/database/vulnerability/fusion-builder/wordpress-avada-builder-plugin-3-11-1-reflected-cross-site-scripting-xss-vulnerability?_s_id=cve"
}
],
"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:L",
"type": "CVSS_V3"
}
]
}
GHSA-9357-FG29-22CV
Vulnerability from github – Published: 2022-05-17 04:59 – Updated: 2022-05-17 04:59Mobile Safari in Apple iOS before 7 does not prevent HTML interpretation of a document served with a text/plain content type, which allows remote attackers to conduct cross-site scripting (XSS) attacks by uploading a file.
{
"affected": [],
"aliases": [
"CVE-2013-5151"
],
"database_specific": {
"cwe_ids": [
"CWE-79"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2013-09-19T10:28:00Z",
"severity": "MODERATE"
},
"details": "Mobile Safari in Apple iOS before 7 does not prevent HTML interpretation of a document served with a text/plain content type, which allows remote attackers to conduct cross-site scripting (XSS) attacks by uploading a file.",
"id": "GHSA-9357-fg29-22cv",
"modified": "2022-05-17T04:59:50Z",
"published": "2022-05-17T04:59:50Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2013-5151"
},
{
"type": "WEB",
"url": "http://lists.apple.com/archives/security-announce/2013/Sep/msg00006.html"
},
{
"type": "WEB",
"url": "http://secunia.com/advisories/54886"
},
{
"type": "WEB",
"url": "http://support.apple.com/kb/HT5934"
},
{
"type": "WEB",
"url": "http://www.securitytracker.com/id/1029054"
}
],
"schema_version": "1.4.0",
"severity": []
}
GHSA-9359-67WF-4FWW
Vulnerability from github – Published: 2022-05-24 16:59 – Updated: 2024-04-04 02:33The weeklynews theme before 2.2.9 for WordPress has XSS via the s parameter.
{
"affected": [],
"aliases": [
"CVE-2015-9504"
],
"database_specific": {
"cwe_ids": [
"CWE-79"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2019-10-23T17:15:00Z",
"severity": "MODERATE"
},
"details": "The weeklynews theme before 2.2.9 for WordPress has XSS via the s parameter.",
"id": "GHSA-9359-67wf-4fww",
"modified": "2024-04-04T02:33:01Z",
"published": "2022-05-24T16:59:39Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2015-9504"
},
{
"type": "WEB",
"url": "https://wpvulndb.com/vulnerabilities/7957"
}
],
"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"
}
]
}
GHSA-935W-GRFP-543V
Vulnerability from github – Published: 2026-03-11 03:31 – Updated: 2026-03-11 03:31Adobe Experience Manager versions 6.5.23 and earlier are affected by a stored Cross-Site Scripting (XSS) vulnerability that could be abused by an attacker to inject malicious scripts into vulnerable form fields. Malicious JavaScript may be executed in a victim’s browser when they browse to the page containing the vulnerable field.
{
"affected": [],
"aliases": [
"CVE-2026-27234"
],
"database_specific": {
"cwe_ids": [
"CWE-79"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-03-11T01:16:53Z",
"severity": "MODERATE"
},
"details": "Adobe Experience Manager versions 6.5.23 and earlier are affected by a stored Cross-Site Scripting (XSS) vulnerability that could be abused by an attacker to inject malicious scripts into vulnerable form fields. Malicious JavaScript may be executed in a victim\u2019s browser when they browse to the page containing the vulnerable field.",
"id": "GHSA-935w-grfp-543v",
"modified": "2026-03-11T03:31:26Z",
"published": "2026-03-11T03:31:26Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-27234"
},
{
"type": "WEB",
"url": "https://helpx.adobe.com/security/products/experience-manager/apsb26-24.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-9369-PQ2M-XXC7
Vulnerability from github – Published: 2022-05-17 02:59 – Updated: 2022-05-17 02:59Cross-site scripting (XSS) vulnerability in squidGuard.cgi in squidGuard before 1.5 allows remote attackers to inject arbitrary web script or HTML via a blocked site link.
{
"affected": [],
"aliases": [
"CVE-2015-8936"
],
"database_specific": {
"cwe_ids": [
"CWE-79"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2017-02-09T15:59:00Z",
"severity": "MODERATE"
},
"details": "Cross-site scripting (XSS) vulnerability in squidGuard.cgi in squidGuard before 1.5 allows remote attackers to inject arbitrary web script or HTML via a blocked site link.",
"id": "GHSA-9369-pq2m-xxc7",
"modified": "2022-05-17T02:59:56Z",
"published": "2022-05-17T02:59:56Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2015-8936"
},
{
"type": "WEB",
"url": "http://www.openwall.com/lists/oss-security/2016/06/20/2"
},
{
"type": "WEB",
"url": "http://www.openwall.com/lists/oss-security/2016/06/20/6"
},
{
"type": "WEB",
"url": "http://www.securityfocus.com/bid/91305"
},
{
"type": "WEB",
"url": "http://www.squidguard.org/Downloads/CHANGELOG"
},
{
"type": "WEB",
"url": "http://www.squidguard.org/Downloads/Patches/1.4/Readme.Patch-20150201"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N",
"type": "CVSS_V3"
}
]
}
Mitigation MIT-4
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
- 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
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
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
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
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
With Struts, write all data from form beans with the bean's filter attribute set to true.
Mitigation MIT-31
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
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
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
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
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.