CVE-2026-65913
Summary
When USE_PROFILES is enabled, DOMPurify rebuilds ALLOWED_ATTR as a plain array before populating it with the requested allowlists. Because the sanitizer still looks up attributes via ALLOWED_ATTR[lcName], any Array.prototype property that is polluted also counts as an allowlisted attribute. An attacker who can set Array.prototype.onclick = true (or a runtime already subject to prototype pollution) can thus force DOMPurify to keep event handlers such as onclick even when they are normally forbidden. The provided PoC sanitizes <img onclick=...> with USE_PROFILES and adds the sanitized output to the DOM; the polluted prototype allows the event handler to survive and execute, turning what should be a blocklist into a silent XSS vector.
Impact
Prototype pollution makes DOMPurify accept dangerous event handler attributes, which bypasses the sanitizer and results in DOM-based XSS once the sanitized markup is rendered.
Credits
Identified by Cantina’s Apex (https://www.cantina.security).
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Exploitation outlook
- Low exploitation risk0.18% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 8% of all EPSS-scored CVEs.
Advisory coverage (2)
External references
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