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.

CVSS 4.0

5.1CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N

CVSS 3.1

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

EPSS

0.2% chance of exploitation in the next 30 days; higher than 11% of CVEs (scores of 2026-10-25)

CWE

CWE-79

Published

2026-07-24

Modified

2026-10-24

Record from

the NVD, synced 2026-10-24

Affected

• cure53:dompurify

Packages (OSV)

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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