CVE-2026-65903: DOMPurify before 3.4.0 ADD_TAGS Function Bypasses FORBID_TAGS

Severity: medium (CVSS 6.1 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2026-07-23 · updated 2026-10-24
Weakness: CWE-697

Description

DOMPurify before 3.4.0 contains a logic error in the ADD_TAGS function where short-circuit evaluation allows forbidden tags to bypass FORBID_TAGS restrictions. Attackers can craft input containing tags listed in FORBID_TAGS that are also added via ADD_TAGS function, causing them to be retained in sanitized output.

Affected products

cure53 DOMPurify: before 3.4.0 — fixed in 3.4.0

How to fix

Upgrade to a fixed version: cure53 DOMPurify 3.4.0. Check the vendor advisory for mitigations.

References

https://github.com/cure53/DOMPurify/security/advisories/GHSA-39q2-94rc-95cp
https://www.vulncheck.com/advisories/dompurify-before-add-tags-function-bypasses-forbid-tags

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