CVE-2026-66010

MEDIUM 6.1

DOMPurify before 3.4.12 Hook Bypass via CUSTOM_ELEMENT_HANDLING

CVSS Score

6.1

EPSS Score

0.0%

EPSS Percentile

0th

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.

CWE	CWE-79
Vendor	cure53
Product	dompurify
Published	Jul 24, 2026
Last Updated	Jul 24, 2026

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CVSS v3 Breakdown

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

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

Required

Scope

Changed

Confidentiality

Low

Integrity

Low

Availability

None

Affected Versions

cure53 / DOMPurify

0 < 3.4.12

References

NVD ↗ CVE.org ↗ EPSS Data ↗

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

Credits

🔍 Rikuxx0