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.
67478 vulnerabilities reference this CWE, most recent first.
GHSA-2QV6-9WX5-CWV4
Vulnerability from github – Published: 2026-05-27 00:09 – Updated: 2026-07-09 21:06Summary
The strip_html filter in liquidjs is intended to remove HTML tags from a string before rendering, and is widely used as an XSS sanitizer. The implementation uses a regex whose catch-all branch (<.*?>) does not match line terminators, so any HTML tag containing a \n or \r character passes through unmodified. An attacker who can place a newline inside a tag (e.g. <img\nsrc=x\nonerror=alert(1)>) bypasses sanitization entirely, since browsers treat newlines as whitespace within a tag and execute the resulting onerror/onload/etc. handler. This results in stored or reflected XSS in any application that relies on strip_html to neutralize untrusted HTML.
Details
The vulnerable code is in src/filters/html.ts:
// src/filters/html.ts:45-49
export function strip_html (this: FilterImpl, v: string) {
const str = stringify(v)
this.context.memoryLimit.use(str.length)
return str.replace(/<script[\s\S]*?<\/script>|<style[\s\S]*?<\/style>|<.*?>|<!--[\s\S]*?-->/g, '')
}
The regex has four alternations:
1. <script[\s\S]*?<\/script> — uses [\s\S], matches across newlines.
2. <style[\s\S]*?<\/style> — uses [\s\S], matches across newlines.
3. <.*?> — uses ., which in JavaScript does not match \n or \r (no s/dotAll flag set).
4. <!--[\s\S]*?--> — uses [\s\S], matches across newlines.
Branch 3 is the catch-all for "any other tag." Because . excludes line terminators, a tag containing a newline does not match any alternative. The literal characters of the tag are passed through to the output.
Browsers, however, parse HTML tag content with whitespace tolerance: per the HTML spec, attribute names and values may be separated by ASCII whitespace, which includes \n and \r. So <img\nsrc=x\nonerror=alert(1)> is parsed as a valid img element with an onerror handler.
liquidjs' default rendering pipeline does not auto-escape filter output (the outputEscape engine option is undefined by default — see src/liquid-options.ts), so the unescaped HTML is delivered verbatim to the consumer's HTML response.
Trust path:
- Application receives untrusted input (e.g. user comment field).
- Developer renders it as {{ comment | strip_html }} to "safely" embed user content as plaintext.
- Attacker submits <img\u000Asrc=x\u000Aonerror=alert(document.cookie)>.
- strip_html returns the input unchanged.
- Output is written into the HTML response with no further escaping.
- Victim's browser executes the attacker's JavaScript in the application's origin.
This is an inconsistency bug: the same regex correctly uses [\s\S] for <script>, <style>, and comment branches, but reverts to . for the catch-all. The other branches' authors clearly knew to handle multi-line content; the catch-all was missed.
PoC
Reproduces against current HEAD (10.25.7) using the published dist/liquid.node.js build:
node -e "
const { Liquid } = require('./dist/liquid.node.js');
const engine = new Liquid();
engine.parseAndRender(
'Safe output: {{ input | strip_html }}',
{ input: '<img\nsrc=x\nonerror=\"alert(document.cookie)\">' }
).then(r => console.log(JSON.stringify(r)));
"
Verified output:
"Safe output: <img\nsrc=x\nonerror=\"alert(document.cookie)\">"
The <img ... onerror=...> tag is delivered to the output completely unmodified. When this string is placed into an HTML document and parsed by a browser, the onerror handler executes.
Same bypass works with \r (carriage return), \r\n, or any combination of CR/LF inside the tag. It also works with other event-handler vectors (<svg\nonload=alert(1)>, <body\nonload=alert(1)>, <iframe\nsrc="javascript:alert(1)">, etc.) and is not specific to <img>.
For comparison, the same input without a newline is correctly stripped:
node -e "
const { Liquid } = require('./dist/liquid.node.js');
const engine = new Liquid();
engine.parseAndRender(
'Safe output: {{ input | strip_html }}',
{ input: '<img src=x onerror=\"alert(1)\">' }
).then(r => console.log(JSON.stringify(r)));
"
# → "Safe output: "
This confirms strip_html is intended to remove tags of this shape, and the newline form is a sanitizer bypass rather than expected behavior.
Impact
Any liquidjs-using application that:
1. Renders attacker-controlled strings via {{ x | strip_html }} to defend against HTML injection, AND
2. Does not separately HTML-escape that output (default behavior — outputEscape is unset by default),
Is vulnerable to stored or reflected XSS. The attacker can execute arbitrary JavaScript in the victim's browser in the application's origin, enabling session theft, account takeover, CSRF with origin-scoped credentials, and arbitrary actions in the victim's authenticated session. The XSS is triggered with simple, well-known event-handler payloads — no exotic encoding, no character set tricks, just a literal newline inside the tag.
The blast radius matches the deployment of liquidjs as a server-side template engine: liquidjs is one of the most popular Liquid implementations on npm (millions of downloads/week) and strip_html is documented as the sanitization filter for HTML stripping, so the vulnerable pattern ({{ user | strip_html }}) is the natural and recommended use of the filter.
Recommended Fix
Replace <.*?> with <[\s\S]*?> (or apply the s/dotAll flag to the entire regex) so the catch-all branch matches across line terminators, consistent with the other branches:
// src/filters/html.ts
export function strip_html (this: FilterImpl, v: string) {
const str = stringify(v)
this.context.memoryLimit.use(str.length)
return str.replace(/<script[\s\S]*?<\/script>|<style[\s\S]*?<\/style>|<[\s\S]*?>|<!--[\s\S]*?-->/g, '')
}
Equivalent fix using the dotAll flag (requires ES2018+, which liquidjs already targets):
return str.replace(/<script.*?<\/script>|<style.*?<\/style>|<.*?>|<!--.*?-->/gs, '')
After the fix, the PoC input is correctly reduced to an empty string. Note that strip_html should still not be relied on as a primary XSS defense — the project README/documentation should recommend HTML-escaping (escape filter) for untrusted content rendered into HTML contexts. A brief security note in the filter's documentation would help users who currently treat strip_html as a sanitizer.
{
"affected": [
{
"package": {
"ecosystem": "npm",
"name": "liquidjs"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"last_affected": "10.25.7"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2026-44644"
],
"database_specific": {
"cwe_ids": [
"CWE-79"
],
"github_reviewed": true,
"github_reviewed_at": "2026-05-27T00:09:12Z",
"nvd_published_at": "2026-06-17T23:17:03Z",
"severity": "MODERATE"
},
"details": "## Summary\n\nThe `strip_html` filter in liquidjs is intended to remove HTML tags from a string before rendering, and is widely used as an XSS sanitizer. The implementation uses a regex whose catch-all branch (`\u003c.*?\u003e`) does not match line terminators, so any HTML tag containing a `\\n` or `\\r` character passes through unmodified. An attacker who can place a newline inside a tag (e.g. `\u003cimg\\nsrc=x\\nonerror=alert(1)\u003e`) bypasses sanitization entirely, since browsers treat newlines as whitespace within a tag and execute the resulting `onerror`/`onload`/etc. handler. This results in stored or reflected XSS in any application that relies on `strip_html` to neutralize untrusted HTML.\n\n## Details\n\nThe vulnerable code is in `src/filters/html.ts`:\n\n```ts\n// src/filters/html.ts:45-49\nexport function strip_html (this: FilterImpl, v: string) {\n const str = stringify(v)\n this.context.memoryLimit.use(str.length)\n return str.replace(/\u003cscript[\\s\\S]*?\u003c\\/script\u003e|\u003cstyle[\\s\\S]*?\u003c\\/style\u003e|\u003c.*?\u003e|\u003c!--[\\s\\S]*?--\u003e/g, \u0027\u0027)\n}\n```\n\nThe regex has four alternations:\n1. `\u003cscript[\\s\\S]*?\u003c\\/script\u003e` \u2014 uses `[\\s\\S]`, matches across newlines.\n2. `\u003cstyle[\\s\\S]*?\u003c\\/style\u003e` \u2014 uses `[\\s\\S]`, matches across newlines.\n3. `\u003c.*?\u003e` \u2014 uses `.`, which in JavaScript does **not** match `\\n` or `\\r` (no `s`/dotAll flag set).\n4. `\u003c!--[\\s\\S]*?--\u003e` \u2014 uses `[\\s\\S]`, matches across newlines.\n\nBranch 3 is the catch-all for \"any other tag.\" Because `.` excludes line terminators, a tag containing a newline does not match any alternative. The literal characters of the tag are passed through to the output.\n\nBrowsers, however, parse HTML tag content with whitespace tolerance: per the HTML spec, attribute names and values may be separated by ASCII whitespace, which includes `\\n` and `\\r`. So `\u003cimg\\nsrc=x\\nonerror=alert(1)\u003e` is parsed as a valid `img` element with an `onerror` handler.\n\n`liquidjs`\u0027 default rendering pipeline does not auto-escape filter output (the `outputEscape` engine option is undefined by default \u2014 see `src/liquid-options.ts`), so the unescaped HTML is delivered verbatim to the consumer\u0027s HTML response.\n\nTrust path:\n- Application receives untrusted input (e.g. user comment field).\n- Developer renders it as `{{ comment | strip_html }}` to \"safely\" embed user content as plaintext.\n- Attacker submits `\u003cimg\\u000Asrc=x\\u000Aonerror=alert(document.cookie)\u003e`.\n- `strip_html` returns the input unchanged.\n- Output is written into the HTML response with no further escaping.\n- Victim\u0027s browser executes the attacker\u0027s JavaScript in the application\u0027s origin.\n\nThis is an inconsistency bug: the same regex correctly uses `[\\s\\S]` for `\u003cscript\u003e`, `\u003cstyle\u003e`, and comment branches, but reverts to `.` for the catch-all. The other branches\u0027 authors clearly knew to handle multi-line content; the catch-all was missed.\n\n## PoC\n\nReproduces against current HEAD (10.25.7) using the published `dist/liquid.node.js` build:\n\n```bash\nnode -e \"\nconst { Liquid } = require(\u0027./dist/liquid.node.js\u0027);\nconst engine = new Liquid();\nengine.parseAndRender(\n \u0027Safe output: {{ input | strip_html }}\u0027,\n { input: \u0027\u003cimg\\nsrc=x\\nonerror=\\\"alert(document.cookie)\\\"\u003e\u0027 }\n).then(r =\u003e console.log(JSON.stringify(r)));\n\"\n```\n\nVerified output:\n\n```\n\"Safe output: \u003cimg\\nsrc=x\\nonerror=\\\"alert(document.cookie)\\\"\u003e\"\n```\n\nThe `\u003cimg ... onerror=...\u003e` tag is delivered to the output completely unmodified. When this string is placed into an HTML document and parsed by a browser, the `onerror` handler executes.\n\nSame bypass works with `\\r` (carriage return), `\\r\\n`, or any combination of CR/LF inside the tag. It also works with other event-handler vectors (`\u003csvg\\nonload=alert(1)\u003e`, `\u003cbody\\nonload=alert(1)\u003e`, `\u003ciframe\\nsrc=\"javascript:alert(1)\"\u003e`, etc.) and is not specific to `\u003cimg\u003e`.\n\nFor comparison, the same input without a newline is correctly stripped:\n\n```bash\nnode -e \"\nconst { Liquid } = require(\u0027./dist/liquid.node.js\u0027);\nconst engine = new Liquid();\nengine.parseAndRender(\n \u0027Safe output: {{ input | strip_html }}\u0027,\n { input: \u0027\u003cimg src=x onerror=\\\"alert(1)\\\"\u003e\u0027 }\n).then(r =\u003e console.log(JSON.stringify(r)));\n\"\n# \u2192 \"Safe output: \"\n```\n\nThis confirms `strip_html` is intended to remove tags of this shape, and the newline form is a sanitizer bypass rather than expected behavior.\n\n## Impact\n\nAny liquidjs-using application that:\n1. Renders attacker-controlled strings via `{{ x | strip_html }}` to defend against HTML injection, AND\n2. Does not separately HTML-escape that output (default behavior \u2014 `outputEscape` is unset by default),\n\nIs vulnerable to stored or reflected XSS. The attacker can execute arbitrary JavaScript in the victim\u0027s browser in the application\u0027s origin, enabling session theft, account takeover, CSRF with origin-scoped credentials, and arbitrary actions in the victim\u0027s authenticated session. The XSS is triggered with simple, well-known event-handler payloads \u2014 no exotic encoding, no character set tricks, just a literal newline inside the tag.\n\nThe blast radius matches the deployment of liquidjs as a server-side template engine: liquidjs is one of the most popular Liquid implementations on npm (millions of downloads/week) and `strip_html` is documented as the sanitization filter for HTML stripping, so the vulnerable pattern (`{{ user | strip_html }}`) is the natural and recommended use of the filter.\n\n## Recommended Fix\n\nReplace `\u003c.*?\u003e` with `\u003c[\\s\\S]*?\u003e` (or apply the `s`/dotAll flag to the entire regex) so the catch-all branch matches across line terminators, consistent with the other branches:\n\n```ts\n// src/filters/html.ts\nexport function strip_html (this: FilterImpl, v: string) {\n const str = stringify(v)\n this.context.memoryLimit.use(str.length)\n return str.replace(/\u003cscript[\\s\\S]*?\u003c\\/script\u003e|\u003cstyle[\\s\\S]*?\u003c\\/style\u003e|\u003c[\\s\\S]*?\u003e|\u003c!--[\\s\\S]*?--\u003e/g, \u0027\u0027)\n}\n```\n\nEquivalent fix using the dotAll flag (requires ES2018+, which liquidjs already targets):\n\n```ts\nreturn str.replace(/\u003cscript.*?\u003c\\/script\u003e|\u003cstyle.*?\u003c\\/style\u003e|\u003c.*?\u003e|\u003c!--.*?--\u003e/gs, \u0027\u0027)\n```\n\nAfter the fix, the PoC input is correctly reduced to an empty string. Note that `strip_html` should still not be relied on as a primary XSS defense \u2014 the project README/documentation should recommend HTML-escaping (`escape` filter) for untrusted content rendered into HTML contexts. A brief security note in the filter\u0027s documentation would help users who currently treat `strip_html` as a sanitizer.",
"id": "GHSA-2qv6-9wx5-cwv4",
"modified": "2026-07-09T21:06:10Z",
"published": "2026-05-27T00:09:12Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/harttle/liquidjs/security/advisories/GHSA-2qv6-9wx5-cwv4"
},
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-44644"
},
{
"type": "WEB",
"url": "https://github.com/harttle/liquidjs/commit/26ea2856c7a90aec892b98d94a9b7a3e18539045"
},
{
"type": "PACKAGE",
"url": "https://github.com/harttle/liquidjs"
},
{
"type": "WEB",
"url": "https://github.com/harttle/liquidjs/releases/tag/v10.26.0"
}
],
"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": "LiquidJS\u0027s strip_html filter bypass via newline characters in HTML tags enables XSS"
}
GHSA-2QV6-C8GQ-2VP7
Vulnerability from github – Published: 2024-05-15 09:31 – Updated: 2026-04-08 21:32The Image Optimization by Optimole – Lazy Load, CDN, Convert WebP & AVIF plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the ‘allow_meme_types’ function in versions up to, and including, 3.12.10 due to insufficient input sanitization and output escaping. This makes it possible for authenticated attackers, with contributor-level permissions and above, to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page.
{
"affected": [],
"aliases": [
"CVE-2024-4636"
],
"database_specific": {
"cwe_ids": [
"CWE-79"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2024-05-15T07:15:48Z",
"severity": "MODERATE"
},
"details": "The Image Optimization by Optimole \u2013 Lazy Load, CDN, Convert WebP \u0026 AVIF plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the \u2018allow_meme_types\u2019 function in versions up to, and including, 3.12.10 due to insufficient input sanitization and output escaping. This makes it possible for authenticated attackers, with contributor-level permissions and above, to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page.",
"id": "GHSA-2qv6-c8gq-2vp7",
"modified": "2026-04-08T21:32:37Z",
"published": "2024-05-15T09:31:51Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2024-4636"
},
{
"type": "WEB",
"url": "https://plugins.trac.wordpress.org/browser/optimole-wp/tags/3.12.10/inc/admin.php#L1828"
},
{
"type": "WEB",
"url": "https://plugins.trac.wordpress.org/changeset/3086306"
},
{
"type": "WEB",
"url": "https://www.wordfence.com/threat-intel/vulnerabilities/id/be88566d-fc84-442d-bb34-834ad9f4465b?source=cve"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N",
"type": "CVSS_V3"
}
]
}
GHSA-2QVF-62MV-JXMQ
Vulnerability from github – Published: 2023-04-18 03:30 – Updated: 2024-04-04 03:31The Thumbnail carousel slider plugin for WordPress is vulnerable to Reflected Cross-Site Scripting via the search_term parameter in versions up to, and including, 1.1.9 due to insufficient input sanitization and output escaping. This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages that execute if they can successfully trick a user into performing an action such as clicking on a link.
{
"affected": [],
"aliases": [
"CVE-2023-2120"
],
"database_specific": {
"cwe_ids": [
"CWE-79"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2023-04-18T02:15:07Z",
"severity": "MODERATE"
},
"details": "The Thumbnail carousel slider plugin for WordPress is vulnerable to Reflected Cross-Site Scripting via the search_term parameter in versions up to, and including, 1.1.9 due to insufficient input sanitization and output escaping. This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages that execute if they can successfully trick a user into performing an action such as clicking on a link.",
"id": "GHSA-2qvf-62mv-jxmq",
"modified": "2024-04-04T03:31:53Z",
"published": "2023-04-18T03:30:42Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2023-2120"
},
{
"type": "WEB",
"url": "https://plugins.trac.wordpress.org/browser/wp-responsive-thumbnail-slider/trunk/wp-responsive-images-thumbnail-slider.php"
},
{
"type": "WEB",
"url": "https://plugins.trac.wordpress.org/changeset?sfp_email=\u0026sfph_mail=\u0026reponame=\u0026old=2813150%40wp-responsive-thumbnail-slider%2Ftags%2F1.1.9\u0026new=2899786%40wp-responsive-thumbnail-slider%2Ftags%2F1.1.10"
},
{
"type": "WEB",
"url": "https://www.wordfence.com/threat-intel/vulnerabilities/id/f4bf4e12-5cbb-45bc-938e-62163baaa15d?source=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:N",
"type": "CVSS_V3"
}
]
}
GHSA-2QVM-65XP-25XH
Vulnerability from github – Published: 2022-05-17 02:04 – Updated: 2022-05-17 02:04Multiple cross-site scripting (XSS) vulnerabilities in the TAM console in IBM Tivoli Access Manager for e-business 6.1.0 before 6.1.0-TIV-TAM-FP0006 allow remote attackers to inject arbitrary web script or HTML via (1) the parm1 parameter to ivt/ivtserver, or the method parameter to (2) acl, (3) domain, (4) group, (5) gso, (6) gsogroup, (7) os, (8) pop, (9) rule, (10) user, or (11) webseal in ibm/wpm/.
{
"affected": [],
"aliases": [
"CVE-2010-4120"
],
"database_specific": {
"cwe_ids": [
"CWE-79"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2010-10-28T21:00:00Z",
"severity": "MODERATE"
},
"details": "Multiple cross-site scripting (XSS) vulnerabilities in the TAM console in IBM Tivoli Access Manager for e-business 6.1.0 before 6.1.0-TIV-TAM-FP0006 allow remote attackers to inject arbitrary web script or HTML via (1) the parm1 parameter to ivt/ivtserver, or the method parameter to (2) acl, (3) domain, (4) group, (5) gso, (6) gsogroup, (7) os, (8) pop, (9) rule, (10) user, or (11) webseal in ibm/wpm/.",
"id": "GHSA-2qvm-65xp-25xh",
"modified": "2022-05-17T02:04:48Z",
"published": "2022-05-17T02:04:48Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2010-4120"
},
{
"type": "WEB",
"url": "https://exchange.xforce.ibmcloud.com/vulnerabilities/62750"
},
{
"type": "WEB",
"url": "http://osvdb.org/68884"
},
{
"type": "WEB",
"url": "http://osvdb.org/68885"
},
{
"type": "WEB",
"url": "http://osvdb.org/68886"
},
{
"type": "WEB",
"url": "http://osvdb.org/68887"
},
{
"type": "WEB",
"url": "http://osvdb.org/68888"
},
{
"type": "WEB",
"url": "http://osvdb.org/68889"
},
{
"type": "WEB",
"url": "http://osvdb.org/68890"
},
{
"type": "WEB",
"url": "http://osvdb.org/68891"
},
{
"type": "WEB",
"url": "http://osvdb.org/68892"
},
{
"type": "WEB",
"url": "http://osvdb.org/68893"
},
{
"type": "WEB",
"url": "http://osvdb.org/68894"
},
{
"type": "WEB",
"url": "http://secunia.com/advisories/41974"
},
{
"type": "WEB",
"url": "http://securitytracker.com/id?1024633"
},
{
"type": "WEB",
"url": "http://www-01.ibm.com/support/docview.wss?uid=swg1IZ84918"
},
{
"type": "WEB",
"url": "http://www.securityfocus.com/bid/44382"
},
{
"type": "WEB",
"url": "http://www.vupen.com/english/advisories/2010/2774"
}
],
"schema_version": "1.4.0",
"severity": []
}
GHSA-2QVP-8C85-3H32
Vulnerability from github – Published: 2023-07-06 21:14 – Updated: 2024-04-04 05:38Auth. (admin+) Stored Cross-Site Scripting (XSS) vulnerability in Thom Stark Eyes Only: User Access Shortcode plugin <= 1.8.2 versions.
{
"affected": [],
"aliases": [
"CVE-2023-25786"
],
"database_specific": {
"cwe_ids": [
"CWE-79"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2023-05-03T11:15:13Z",
"severity": "MODERATE"
},
"details": "Auth. (admin+) Stored Cross-Site Scripting (XSS) vulnerability in Thom Stark Eyes Only: User Access Shortcode plugin \u003c=\u00a01.8.2 versions.",
"id": "GHSA-2qvp-8c85-3h32",
"modified": "2024-04-04T05:38:42Z",
"published": "2023-07-06T21:14:53Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2023-25786"
},
{
"type": "WEB",
"url": "https://patchstack.com/database/vulnerability/eyes-only-user-access-shortcode/wordpress-eyes-only-user-access-shortcode-plugin-1-8-2-cross-site-scripting-xss?_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-2QVQ-RJWJ-GVW9
Vulnerability from github – Published: 2026-03-26 22:20 – Updated: 2026-03-27 21:52Summary
resolvePartial() in the Handlebars runtime resolves partial names via a plain property lookup on options.partials without guarding against prototype-chain traversal. When Object.prototype has been polluted with a string value whose key matches a partial reference in a template, the polluted string is used as the partial body and rendered without HTML escaping, resulting in reflected or stored XSS.
Description
The root cause is in lib/handlebars/runtime.js inside resolvePartial() and invokePartial():
// Vulnerable: plain bracket access traverses Object.prototype
partial = options.partials[options.name];
hasOwnProperty is never checked, so if Object.prototype has been seeded with a key whose name matches a partial reference in the template (e.g. widget), the lookup succeeds and the polluted string is returned. The runtime emits a prototype-access warning, but the partial is still resolved and its content is inserted into the rendered output unescaped. This contradicts the documented security model and is distinct from CVE-2021-23369 and CVE-2021-23383, which addressed data property access rather than partial template resolution.
Prerequisites for exploitation:
1. The target application must be vulnerable to prototype pollution (e.g. via qs, minimist, or
any querystring/JSON merge sink).
2. The attacker must know or guess the name of a partial reference used in a template.
Proof of Concept
const Handlebars = require('handlebars');
// Step 1: Prototype pollution (via qs, minimist, or another vector)
Object.prototype.widget = '<img src=x onerror="alert(document.domain)">';
// Step 2: Normal template that references a partial
const template = Handlebars.compile('<div>Welcome! {{> widget}}</div>');
// Step 3: Render — XSS payload injected unescaped
const output = template({});
// Output: <div>Welcome! <img src=x onerror="alert(document.domain)"></div>
The runtime prints a prototype access warning claiming "access has been denied," but the partial still resolves and returns the polluted value.
Workarounds
- Apply
Object.freeze(Object.prototype)early in application startup to prevent prototype pollution. Note: this may break other libraries. - Use the Handlebars runtime-only build (
handlebars/runtime), which does not compile templates and reduces the attack surface.
{
"affected": [
{
"package": {
"ecosystem": "npm",
"name": "handlebars"
},
"ranges": [
{
"events": [
{
"introduced": "4.0.0"
},
{
"fixed": "4.7.9"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2026-33916"
],
"database_specific": {
"cwe_ids": [
"CWE-1321",
"CWE-79"
],
"github_reviewed": true,
"github_reviewed_at": "2026-03-26T22:20:51Z",
"nvd_published_at": "2026-03-27T21:17:27Z",
"severity": "MODERATE"
},
"details": "## Summary\n\n`resolvePartial()` in the Handlebars runtime resolves partial names via a plain property lookup on `options.partials` without guarding against prototype-chain traversal. When `Object.prototype` has been polluted with a string value whose key matches a partial reference in a template, the polluted string is used as the partial body and rendered **without HTML escaping**, resulting in reflected or stored XSS.\n\n## Description\n\nThe root cause is in `lib/handlebars/runtime.js` inside `resolvePartial()` and `invokePartial()`:\n\n```javascript\n// Vulnerable: plain bracket access traverses Object.prototype\npartial = options.partials[options.name];\n```\n\n`hasOwnProperty` is never checked, so if `Object.prototype` has been seeded with a key whose name matches a partial reference in the template (e.g. `widget`), the lookup succeeds and the polluted string is returned. The runtime emits a prototype-access warning, but the partial is still resolved and its content is inserted into the rendered output unescaped. This contradicts the documented security model and is distinct from CVE-2021-23369 and CVE-2021-23383, which addressed data property access rather than partial template resolution.\n\n**Prerequisites for exploitation:**\n1. The target application must be vulnerable to prototype pollution (e.g. via `qs`, `minimist`, or\n any querystring/JSON merge sink).\n2. The attacker must know or guess the name of a partial reference used in a template.\n\n## Proof of Concept\n\n```javascript\nconst Handlebars = require(\u0027handlebars\u0027);\n\n// Step 1: Prototype pollution (via qs, minimist, or another vector)\nObject.prototype.widget = \u0027\u003cimg src=x onerror=\"alert(document.domain)\"\u003e\u0027;\n\n// Step 2: Normal template that references a partial\nconst template = Handlebars.compile(\u0027\u003cdiv\u003eWelcome! {{\u003e widget}}\u003c/div\u003e\u0027);\n\n// Step 3: Render \u2014 XSS payload injected unescaped\nconst output = template({});\n// Output: \u003cdiv\u003eWelcome! \u003cimg src=x onerror=\"alert(document.domain)\"\u003e\u003c/div\u003e\n```\n\n\u003e The runtime prints a prototype access warning claiming \"access has been denied,\" but the partial still resolves and returns the polluted value.\n\n## Workarounds\n\n- Apply `Object.freeze(Object.prototype)` early in application startup to prevent prototype pollution. Note: this may break other libraries.\n- Use the Handlebars runtime-only build (`handlebars/runtime`), which does not compile templates and reduces the attack surface.",
"id": "GHSA-2qvq-rjwj-gvw9",
"modified": "2026-03-27T21:52:02Z",
"published": "2026-03-26T22:20:51Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/handlebars-lang/handlebars.js/security/advisories/GHSA-2qvq-rjwj-gvw9"
},
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2021-23369"
},
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2021-23383"
},
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-33916"
},
{
"type": "WEB",
"url": "https://github.com/handlebars-lang/handlebars.js/commit/68d8df5a88e0a26fe9e6084c5c6aaebe67b07da2"
},
{
"type": "PACKAGE",
"url": "https://github.com/handlebars-lang/handlebars.js"
},
{
"type": "WEB",
"url": "https://github.com/handlebars-lang/handlebars.js/releases/tag/v4.7.9"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:L/I:L/A:N",
"type": "CVSS_V3"
}
],
"summary": "Handlebars.js has Prototype Pollution Leading to XSS through Partial Template Injection"
}
GHSA-2QVW-44PQ-38XJ
Vulnerability from github – Published: 2025-04-17 06:30 – Updated: 2025-04-17 21:30The Ultimate Dashboard WordPress plugin before 3.8.6 does not sanitise and escape some of its settings, which could allow high privilege users such as admin to perform Stored Cross-Site Scripting attacks even when the unfiltered_html capability is disallowed (for example in multisite setup).
{
"affected": [],
"aliases": [
"CVE-2025-1525"
],
"database_specific": {
"cwe_ids": [
"CWE-79"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2025-04-17T06:15:43Z",
"severity": "LOW"
},
"details": "The Ultimate Dashboard WordPress plugin before 3.8.6 does not sanitise and escape some of its settings, which could allow high privilege users such as admin to perform Stored Cross-Site Scripting attacks even when the unfiltered_html capability is disallowed (for example in multisite setup).",
"id": "GHSA-2qvw-44pq-38xj",
"modified": "2025-04-17T21:30:54Z",
"published": "2025-04-17T06:30:35Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2025-1525"
},
{
"type": "WEB",
"url": "https://wpscan.com/vulnerability/d457733f-72e9-45e2-ac07-4e1b94e46102"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:U/C:L/I:L/A:N",
"type": "CVSS_V3"
}
]
}
GHSA-2QW3-J5GW-6H65
Vulnerability from github – Published: 2022-05-17 01:42 – Updated: 2022-05-17 01:42Cross-site scripting (XSS) vulnerability in tokyo_bbs.cgi in Come on Girls Interface (CGI) Tokyo BBS allows remote attackers to inject arbitrary web script or HTML via vectors related to the error page.
{
"affected": [],
"aliases": [
"CVE-2012-4019"
],
"database_specific": {
"cwe_ids": [
"CWE-79"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2012-10-26T10:39:00Z",
"severity": "MODERATE"
},
"details": "Cross-site scripting (XSS) vulnerability in tokyo_bbs.cgi in Come on Girls Interface (CGI) Tokyo BBS allows remote attackers to inject arbitrary web script or HTML via vectors related to the error page.",
"id": "GHSA-2qw3-j5gw-6h65",
"modified": "2022-05-17T01:42:46Z",
"published": "2022-05-17T01:42:46Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2012-4019"
},
{
"type": "WEB",
"url": "https://exchange.xforce.ibmcloud.com/vulnerabilities/79633"
},
{
"type": "WEB",
"url": "http://jvn.jp/en/jp/JVN00322303/995209/index.html"
},
{
"type": "WEB",
"url": "http://jvn.jp/en/jp/JVN00322303/index.html"
},
{
"type": "WEB",
"url": "http://jvndb.jvn.jp/jvndb/JVNDB-2012-000093"
},
{
"type": "WEB",
"url": "http://osvdb.org/86722"
}
],
"schema_version": "1.4.0",
"severity": []
}
GHSA-2QWC-C9M4-M7FX
Vulnerability from github – Published: 2022-05-17 00:34 – Updated: 2022-05-17 00:34IBM RELM 4.0, 5.0, and 6.0 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: 126243.
{
"affected": [],
"aliases": [
"CVE-2017-1335"
],
"database_specific": {
"cwe_ids": [
"CWE-79"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2017-10-03T01:29:00Z",
"severity": "MODERATE"
},
"details": "IBM RELM 4.0, 5.0, and 6.0 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: 126243.",
"id": "GHSA-2qwc-c9m4-m7fx",
"modified": "2022-05-17T00:34:18Z",
"published": "2022-05-17T00:34:18Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2017-1335"
},
{
"type": "WEB",
"url": "https://exchange.xforce.ibmcloud.com/vulnerabilities/126243"
},
{
"type": "WEB",
"url": "http://www.ibm.com/support/docview.wss?uid=swg22008785"
},
{
"type": "WEB",
"url": "http://www.securityfocus.com/bid/101062"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:3.0/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N",
"type": "CVSS_V3"
}
]
}
GHSA-2QWH-3HFV-WJ79
Vulnerability from github – Published: 2026-07-02 12:31 – Updated: 2026-07-02 12:31Unauthenticated Cross Site Scripting (XSS) in TheFox <= 3.9.76 versions.
{
"affected": [],
"aliases": [
"CVE-2026-27430"
],
"database_specific": {
"cwe_ids": [
"CWE-79"
],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-07-02T12:17:00Z",
"severity": "HIGH"
},
"details": "Unauthenticated Cross Site Scripting (XSS) in TheFox \u003c= 3.9.76 versions.",
"id": "GHSA-2qwh-3hfv-wj79",
"modified": "2026-07-02T12:31:00Z",
"published": "2026-07-02T12:31:00Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-27430"
},
{
"type": "WEB",
"url": "https://patchstack.com/database/wordpress/theme/thefox/vulnerability/wordpress-thefox-theme-3-9-76-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"
}
]
}
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.