GHSA-x3q4-9hxx-gx8m - ApostropheCMS sanitize-html: nonTextTags discard region ends early on an implied close, letting <noscript> content render
## Summary
`sanitize-html` discards the *content* of every element in `nonTextTags`. It delimits that region
using htmlparser2's close events, and ignores the `isImplied` flag htmlparser2 passes it. Closing a
still-open **ancestor** from inside a `<noscript>` makes htmlparser2 unwind its stack past the
`noscript`; the synthetic implied close it emits on the way ends the discard region early, and
everything after it is treated as ordinary body content.
A browser with scripting enabled parses `<noscript>` content as **raw text**, so the same markup
renders as inert text there. The sanitizer therefore emits elements the page itself would not have.
## Reproduction
```js
const sanitizeHtml = require("sanitize-html");
sanitizeHtml('<div><noscript></div><img src="http://evil.test/t.gif"></noscript>', {
allowedTags: ["div", "img"],
allowedAttributes: { img: ["src"] },
nonTextTags: ["script", "style", "textarea", "option", "noscript"],
});
// => '<div></div><img src="http://evil.test/t.gif" />'
```
Chrome, given the same input, renders **no** `<img>` โ the whole payload is raw text inside the
unclosed `<noscript>`. Verified with Playwright, `srcdoc` into an iframe so the scripting flag is on.
A `<![CDATA[` variant hides the opening tag from the parser entirely and has the same effect:
```
<p>Hi</p><![CDATA[ x > <noscript>]]><a href="โฆ">Reset your password</a><img src="โฆbeacon.gif"></noscript>
```
htmlparser2 runs a CDATA token to `]]>`; Chrome ends a bogus comment at the first `>`, so the
`<noscript>` after it is real to the browser and invisible to the parser.
## Where the behaviour is
`index.js`:
- `:154` โ `nonTextTagsArray` (the default list, `['script','style','textarea','option','xmp']`).
- `:638` โ `onclosetag: function (name, isImplied)` โ receives the flag.
- `:644` โ `skipTextDepth--` โ decrements without consulting `isImplied`.
## Suggested fix
Do not end a discard region on an implied close. htmlparser2 already distinguishes them; the flag
is
MEDIUM
Severity & confidence
Source severitymedium
Platform severitymedium
Confidencehigh
Exploitationunknown
CVSS-
Affected
Vendorssanitize-htmlRed Hat
Productssanitize-html
Reporting sources (2)
GitHub Security Advisories
Red Hat - CVE Feed
Timeline & provenance
Published2026-10-20T18:03:22
Last updated2026-10-21T07:49:06
Ingested2026-10-20T18:05:01
FreshnessNEAR-REAL-TIME
Threat typeadvisory
Recommended action
Review the advisory and upgrade affected packages to the first patched version.
Next steps
- Identify affected systems in your environment.
- Apply the vendor patch or mitigation guidance.
- Review logs for indicators described in the advisory.
- Follow the affected vendor/product to track updates.
Confidence explanation
Reported by a government or cert-grade source (CISA, NCSC, NVD, ENISA, MSRC).
Source type: vendor ยท Original: GitHub Security Advisories