Vulnerability · Published Jul 24, 2026 · Assigned by VulnCheck

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

Medium 6.1

In plain English

A medium-severity cross-site scripting in DOMPurify from cure53. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 12% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)6.1Medium

Exploit odds (30 days)0.2%top 88.0% of all CVEs

Exploited in the wildNo reportsCISA SSVC: poc

Attack toolingNoneno public tooling known

Official 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 packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
Debian:12	node-dompurify	no fix listed	DEBIAN-CVE-2026-66010
Debian:13	node-dompurify	no fix listed	DEBIAN-CVE-2026-66010
Debian:14	node-dompurify	3.4.12+dfsg-1	DEBIAN-CVE-2026-66010
Ubuntu:22.04:LTS	node-dompurify	no fix listed	UBUNTU-CVE-2026-66010
Ubuntu:24.04:LTS	node-dompurify	no fix listed	UBUNTU-CVE-2026-66010
Ubuntu:26.04:LTS	node-dompurify	no fix listed	UBUNTU-CVE-2026-66010
npm	dompurify	3.4.12	GHSA-c2j3-45gr-mqc4

Affected products (as reported)

Vendor	Product	Versions
cure53	DOMPurify	0 – before 3.4.12

Weakness: CWE-79 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

References

GitHub Security Advisory (GHSA-c2j3-45gr-mqc4) vendor-advisory
VulnCheck Advisory: DOMPurify before 3.4.12 Hook Bypass via CUSTOM_ELEMENT_HANDLING third-party-advisory