What’s Vulnerable › Vulnerabilities

CVE-2026-65911: DOMPurify before 3.4.0 XSS via ADD_ATTR/ADD_TAGS State Leakage

• 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-79

Description

In DOMPurify through 3.3.3, function predicates supplied via ADD_ATTR or ADD_TAGS to DOMPurify.sanitize() persist in internal state (EXTRA_ELEMENT_HANDLING) across subsequent sanitize() calls on the same instance. If a later call on the same instance provides ADD_ATTR or ADD_TAGS as an array rather than a function, the previously set function handler is neither cleared nor overwritten, so it continues to approve attacker-controlled attributes or tags. This can allow dangerous event-handler attributes or forbidden tags (bypassing FORBID_TAGS) to survive sanitization, resulting in cross-site scripting. The vendor (Cure53) considers this an edge case outside DOMPurify's threat model; the referenced advisory lists 3.4.0 as the patched version.

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-9p3w-6h5p-cv75
• https://www.vulncheck.com/advisories/dompurify-before-xss-via-add-attr-add-tags-state-leakage

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