xhtml-purifier has HTML attribute-injection (sanitizer bypass) that leads to XSS

Exploitation

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

CVSS

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

EPSS

• CVE-2026-61784: 0.18% estimated exploitation activity in the next 30 days; percentile 7.37 (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.

xhtml-purifier does not HTML-entity-encode attribute values when serializing its sanitized output. In attributeString() (XHTMLPurifier.js, around line 148) the attribute value is concatenated directly into a double-quoted attribute without encoding. As a result, an attacker-controlled value in any allowed attribute (class, style, title, alt, src, href) can include a double-quote character to break out of the attribute and inject an additional attribute, such as a JavaScript event handler (for example onmouseover or onerror). The injected handler survives sanitization and executes when the output is rendered, which is a sanitizer bypass leading to cross-site scripting. The fix HTML-entity-encodes attribute values before serialization.

Published by the source

24 Sep 2026, 19:33 UTC

Last modified by the source

24 Sep 2026, 19:45 UTC

Source last checked

26 Oct 2026, 13:02 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-j8r4-32c5-33rc

2. Revision 2 · amended · 24 Oct 2026

   Amended from osv record GHSA-j8r4-32c5-33rc

3. Revision 1 · created · 23 Oct 2026

   Published from ghsa record GHSA-j8r4-32c5-33rc

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# Patch Next advisory brief: CVE-2026-61784

Advisory: xhtml-purifier has HTML attribute-injection (sanitizer bypass) that leads to XSS
IDs: CVE-2026-61784, GHSA-j8r4-32c5-33rc
Record: https://patchnext.com/advisories/cve-2026-61784 (revision 3, source checked 26 Oct 2026, 13:02 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.1)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: xhtml-purifier 0.4.3. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm xhtml-purifier: affected <= 0.4.1; fixed in 0.4.3

## Suggested inspection (read-only)
- `npm ls xhtml-purifier --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 xhtml-purifier.
- 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-j8r4-32c5-33rc (GitHub-reviewed advisory GHSA-j8r4-32c5-33rc lists affected ranges: npm xhtml-purifier >=0 <=0.4.1)
- Verified: https://osv.dev/vulnerability/GHSA-j8r4-32c5-33rc (OSV record GHSA-j8r4-32c5-33rc lists affected ranges: npm xhtml-purifier >=0 <0.4.3 (fixed))

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