fix(deps): update dependency sanitize-html to v2.17.7 [security]

[renovate]

This PR contains the following updates:

Package	Change	Age	Confidence
sanitize-html (source)	2.17.6 → 2.17.7

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ApostropheCMS: Stored XSS via SVG SMIL URI-list scheme-policy bypass

CVE-2026-84371 / GHSA-g8qq-57p8-ggw5

More information

Details

Summary

When SVG animation is allowed, attributeName="href" makes values a list of URL destinations. sanitize-html accepts a list that starts with a safe fragment even when values is explicitly scheme-checked, allowing a later javascript: destination to execute when the sanitized link is activated.

Details

index.js:371-383 validates each attribute as one flat URL. It does not recognize that attributeName="href" gives the sibling values attribute SMIL URI-list semantics. For values="#safe;javascript:...", the leading fragment passes the flat check and the complete list is retained.

PoC

This was reproduced with sanitize-html@2.17.6 and Chromium 150.0.7871.124. The configuration adds SVG animation to the defaults and applies the existing scheme policy to values; it does not allow javascript:. Save this as poc.js:

const sanitize = require('sanitize-html');

const input = `<svg><a><animate attributeName="href" values="#safe;javascript:alert('XSS')" dur=".01s" fill="freeze"></animate><text y="30">Click me</text></a></svg>`;
const output = sanitize(input, {
  allowedTags: sanitize.defaults.allowedTags.concat(['svg', 'animate', 'text']),
  allowedAttributes: {
    ...sanitize.defaults.allowedAttributes,
    animate: ['attributename', 'values', 'dur', 'fill'],
    text: ['y']
  },
  allowedSchemesAppliedToAttributes:
    sanitize.defaults.allowedSchemesAppliedToAttributes.concat(['values'])
});
console.log(output);

Install and run it, then open poc.html and click Click me:

npm install sanitize-html@2.17.6
node poc.js > poc.html

The output retains the javascript: entry, and clicking the sanitized SVG displays XSS. With input changed to <a href="javascript:alert(1)">control</a>, the same configuration removes href.

Impact

In an application that accepts attacker-authored SVG animation, the attacker can store this payload without scripts or event handlers. A victim who activates the sanitized link executes JavaScript in the application's origin despite the configured scheme policy.

Suggested fix

Reject attributeName values selecting href or xlink:href on SVG animate and set, while retaining safe targets such as fill. Add values, from, and to regression cases.

Severity

• CVSS Score: 5.4 / 10 (Medium)
• Vector String: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N

References

• https://github.com/apostrophecms/apostrophe/security/advisories/GHSA-g8qq-57p8-ggw5
• https://github.com/apostrophecms/apostrophe/pull/5552
• https://github.com/apostrophecms/apostrophe/commit/1135516a1a4a8f9638641c460488a43d8af20081
• https://github.com/apostrophecms/apostrophe/commit/38ff1106c8176b16c2da9872acd9b449adcbb949
• https://github.com/apostrophecms/apostrophe/blob/main/packages/sanitize-html/CHANGELOG.md
• https://github.com/advisories/GHSA-g8qq-57p8-ggw5

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

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Release Notes

apostrophecms/apostrophe (sanitize-html)

v2.17.7

Security

• Fixed an XSS / URL scheme policy bypass affecting configurations that allow the SVG animation elements (animate, animateColor, animateMotion, animateTransform or set) together with attributeName and one of the animation value attributes. The default configuration was not affected, as these elements are not in the default allowedTags. apostrophecms was not affected. Thanks to koyokr for responsibly disclosing the vulnerability (GHSA-g8qq-57p8-ggw5).

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