vulnerability / NVI-00016452 / Revision 1
ApostropheCMS: Stored XSS via SVG SMIL URI-list scheme-policy bypass
GitHub lists this reviewed advisory for sanitize-html. Published version ranges and source prerequisites are shown below; this is not an inspection of a visitor’s application.
This report has not inspected your inventory, configuration, deployed build, reachability or evidence. A catalog listing and a severity score do not establish exposure or compromise.
01 / Meaning
Why it matters
Published affected context helps an owner decide what evidence to gather. This report has not examined your application.
5.4 medium
GitHub source severity; exploitability and local consequence require separate evidence.
As of · GitHub Advisory Database
02 / Applicability
The affected context
Affected versions, configuration prerequisites and known exclusions are public. Confirm each one against the deployed service.
sanitize-html
source listed>= 1.9.0, <= 2.17.6
### 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 = `Click me`; const output = sanitize(input, { allowedTags: sanitize.defaults.allowedTags.concat(['svg', 'animate', 'text']), all
03 / Response
What to do next
- investigate
Identify the exact component and deployed version, examine the linked publisher’s conditions, and retain evidence of any mitigation.
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04 / Limits
What this report cannot establish
- Customer inventory, deployment, reachability and exploitation have not been inspected.
05 / Provenance
Sources you can inspect
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- GHSA-g8qq-57p8-ggw5 ↗
GitHub Advisory Database · vendor advisory
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Public revision history
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- Revision 1 ·
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