DOMPurify: IN_PLACE hook removal leaves a detached subtree executable, causing XSS

Exploitation

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

CVSS 4.0

5.1 · CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N · score source

EPSS

No dated EPSS signal available.

As published by the source; long descriptions are shortened.

Summary During INPLACE sanitization, a hook that removes an element can leave that element's detached descendants executable. A descendant image can retain its attacker-provided onload handler and fire after sanitize() returns, even though the returned root is clean and the image remains disconnected from the document. Details In DOMPurify 3.4.12, sanitizeElements() in src/purify.ts:1862-1904 runs the beforeSanitizeElements or uponSanitizeElement hook and returns immediately when the hook detached the current node. The return does not call neutralizeSubtree(currentNode). The detached subtree is not added to DOMPurify.removed, so the post-walk INPLACE neutralization cannot reach it. If the browser queued a resource event while the application constructed the detached dirty root, a descendant can therefore retain its handler and execute after sanitization. The hook only rejects the containing element and does not add or approve the event handler. DOMPurify's ordinary removal path…

Published by the source

7 Aug 2026, 15:30 UTC

Last modified by the source

7 Aug 2026, 15:30 UTC

Source last checked

26 Oct 2026, 13:00 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-55q2-fjhq-7xh7

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: GHSA-55q2-fjhq-7xh7

Advisory: DOMPurify: IN_PLACE hook removal leaves a detached subtree executable, causing XSS
IDs: GHSA-55q2-fjhq-7xh7
Record: https://patchnext.com/advisories/ghsa-55q2-fjhq-7xh7 (revision 1, source checked 26 Oct 2026, 13:00 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.1)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: dompurify 3.4.13. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm dompurify: affected <= 3.4.12; fixed in 3.4.13

## Suggested inspection (read-only)
- `npm ls dompurify --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 dompurify.
- 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-55q2-fjhq-7xh7 (GitHub-reviewed advisory GHSA-55q2-fjhq-7xh7 lists affected ranges: npm dompurify >=0 <=3.4.12)

Commands are suggestions: review each one before running it.