What’s Vulnerable › Vulnerabilities

CVE-2026-66010: DOMPurify before 3.4.12 Hook Bypass via CUSTOM_ELEMENT_HANDLING

• Severity: medium (CVSS 6.1 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2026-07-24 · updated 2026-10-24
• Weakness: CWE-79

Description

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.

Affected products

• cure53 DOMPurify: before 3.4.12 — fixed in 3.4.12

How to fix

Upgrade to a fixed version: cure53 DOMPurify 3.4.12. Check the vendor advisory for mitigations.

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
• https://github.com/cure53/DOMPurify/security/advisories/GHSA-c2j3-45gr-mqc4

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