Apostrophe has default XSS via xmp raw-text passthrough in sanitize-html

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

9.3 · CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N

EPSS

• CVE-2026-44990: 0.68% estimated exploitation activity in the next 30 days; percentile 52.61 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary Under the default configuration, sanitize-html can turn attacker-controlled content inside a disallowed xmp element into live HTML or JavaScript. This is a sanitizer bypass in the default disallowedTagsMode: 'discard' path and can lead to stored XSS in applications that render sanitized output back to users. Details In sanitize-html@2.17.3, the default nonTextTags list includes only script, style, textarea, and option in index.js lines 138-142. That means disallowed xmp tags are not treated as "drop the entire contents" tags. Later, in the ontext handler at index.js lines 569-577, the code special-cases textarea and xmp and appends their text content directly to the output without escaping: Because htmlparser2 treats xmp as a raw-text element, markup inside xmp is parsed as text on input but becomes live markup again once it is appended unescaped to the sanitized output. This creates a default sanitizer bypass. For example, a disallowed <xmp wrapper can be used to smuggle…

Published by the source

14 May 2026, 18:26 UTC

Last modified by the source

12 Jun 2026, 22:15 UTC

Source last checked

26 Oct 2026, 12:55 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-rpr9-rxv7-x643

2. Revision 2 · amended · 24 Oct 2026

   Amended from osv record GHSA-rpr9-rxv7-x643

3. Revision 1 · created · 23 Oct 2026

   Published from ghsa record GHSA-rpr9-rxv7-x643

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# Patch Next advisory brief: CVE-2026-44990

Advisory: Apostrophe has default XSS via `xmp` raw-text passthrough in `sanitize-html`
IDs: CVE-2026-44990, GHSA-rpr9-rxv7-x643
Record: https://patchnext.com/advisories/cve-2026-44990 (revision 3, source checked 26 Oct 2026, 12:55 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Critical (CVSS 9.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: sanitize-html 2.17.4. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm sanitize-html: affected >= 2.17.3, <= 2.17.3; fixed in 2.17.4

## Suggested inspection (read-only)
- `npm ls sanitize-html --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on sanitize-html.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-rpr9-rxv7-x643 (GitHub-reviewed advisory GHSA-rpr9-rxv7-x643 lists affected ranges: npm sanitize-html >=2.17.3 <=2.17.3)
- Verified: https://osv.dev/vulnerability/GHSA-rpr9-rxv7-x643 (OSV record GHSA-rpr9-rxv7-x643 lists affected ranges: npm sanitize-html >=2.17.3 <2.17.4 (fixed))

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