# DOMPurify SMIL attributeName=href guard bypass in XHTML mode

Source: https://junglewise.ai/threats/dompurify-smil-attributename-href-guard-is-skipped-when-parser-media-15a5efd2  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-22. Updated: 2026-10-22  
License: CC BY 4.0 with a link back

Severity: low · Published 2026-10-22

DOMPurify is a library that sanitizes HTML and SVG content to prevent cross-site scripting attacks. When configured to parse XHTML documents and allow SVG animation elements, DOMPurify fails to block a dangerous attributeName="href" attribute that can inject malicious JavaScript. An attacker can craft an SVG that modifies a link's target to execute JavaScript when clicked.

Technologies: [Cure53 DOMPurify](https://junglewise.ai/threats/technologies/cure53-dompurify), [dompurify (npm)](https://junglewise.ai/threats/technologies/dompurify). Vendors: [Cure53](https://junglewise.ai/threats/vendors/cure53), [npm](https://junglewise.ai/threats/vendors/npm).

## Quick answers

**Is This vulnerability exploited in the wild?** No. Junglewise Threat Intelligence has no report of This vulnerability being exploited in the wild.

**How severe is This vulnerability?** Low severity, published 22 October 2026.

**Which products and versions are affected?** Cure53 DOMPurify <=3.4.16; dompurify (npm) <= 3.4.16, SEMVER:introduced=0,fixed=3.4.17.

**Is there a fix for This vulnerability?** Yes. dompurify (npm): upgrade to 3.4.17 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is This vulnerability attacked?** It is attacked over the network, in a software library.

**Am I affected?** Check whether you run Cure53 DOMPurify or dompurify (npm) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- dompurify (npm): upgrade to 3.4.17 or later

  ```sh
  npm install dompurify@3.4.17
  ```


## Technical details

The vulnerability is a case-sensitivity bypass in the attributeName=href guard when PARSER_MEDIA_TYPE is set to 'application/xhtml+xml'. In XHTML mode, the transformCaseFunc does not lowercase attribute names (preserving XML case-sensitivity), so the check comparing lcName === "attributename" fails when the actual attribute is "attributeName". This allows SMIL animate/set elements with attributeName="href" and malicious values to pass through; with fill="freeze", the semicolon-delimited values syntax causes the JavaScript URI to become the effective href of the parent link.

## Affected products

- cure53 DOMPurify <=3.4.16

## Timeline

- 2026-10-22: disclosed
- 2026-10-12: advisory
- 2026-10-22: patched: fix in version 3.4.17

## References

- [https://github.com/cure53/DOMPurify/security/advisories/GHSA-c6gr-qvv4-5v3f](https://github.com/cure53/DOMPurify/security/advisories/GHSA-c6gr-qvv4-5v3f)
- [https://github.com/cure53/DOMPurify/pull/1672](https://github.com/cure53/DOMPurify/pull/1672)

## Related threats

- [DOMPurify SAFE_FOR_TEMPLATES bypass via shadow root content](https://junglewise.ai/threats/cve-2026-116804-dompurify-from-3-4-4-before-3-4-17-contains-a-safe-for-templates)
- [DOMPurify DOM XSS in IN_PLACE hook-detached subtrees](https://junglewise.ai/threats/cve-2026-116803-dompurify-before-3-4-17-contains-a-cross-site-scripting)
- [DOMPurify cross-site scripting in SMIL attributeName guard bypass](https://junglewise.ai/threats/cve-2026-116802-dompurify-before-3-4-17-contains-a-cross-site-scripting)
- [DOMPurify SAFE_FOR_TEMPLATES bypass in shadow root content](https://junglewise.ai/threats/dompurify-safe-for-templates-bypass-split-template-expressions-survive-c23665cf)
- [DOMPurify IN_PLACE event handler bypass when hook removes parent or sibling](https://junglewise.ai/threats/dompurify-in-place-hook-that-removes-a-parent-or-sibling-leaves-the-3ea5d18f)