CVE-2026-66010

DOMPurify before 3.4.12 fails to execute afterSanitizeElements hook for custom elements allowed via CUSTOM_ELEMENT_HANDLING.tagNameCheck, allowing attributes to bypass application security policies. Attackers can preserve sensitive attributes on custom elements that later re-inject them into innerHTML sinks, creating second-order XSS gadgets.

Score

CVSS 3.1 6.1 Medium

Status

Analyzed - disclosure@vulncheck.com

Published

2026-07-24

Last modified

2026-10-24

Weaknesses

CWE-79

Affected products

• Dompurify (Cure53)

References

• https://github.com/cure53/DOMPurify/security/advisories/GHSA-c2j3-45gr-mqc4
• https://www.vulncheck.com/advisories/dompurify-before-hook-bypass-via-custom-element-handling