Medium severity · published Jul 24, 2026
CVE-2026-66010
DOMPurify before 3.4.12 Hook Bypass via CUSTOM_ELEMENT_HANDLING
6.1
CVSS
0.2%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
Required
Confidentiality
Low
Integrity
Low
Availability
None
Scope
Changed
Exploitation
Is it being used?
Exploit prediction (EPSS)0.2% · higher than 12% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
DO
DOMPurify · cure53
before 3.4.12 · source: vendor, NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-66010
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-66010
Exploit
https://github.com/cure53/DOMPurify/security/advisories/GHSA-c2j3-45gr-mqc4
Third Party Advisory
https://www.vulncheck.com/advisories/dompurify-before-hook-bypass-via-custom-element-handling
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