CVE-2026-65904: CURE53 Dompurify

Medium severity, CVSS 4.7. EPSS: 0.3% chance of exploitation in the next 30 days.

DOMPurify through 3.3.3 fails to sanitize DOM elements passed via IN_PLACE mode when the element originates from a different window/realm (e.g., an iframe's contentDocument). A cross-realm instanceof check in the private _isNode() function returns false for foreign-realm nodes, causing DOMPurify to stringify the element (yielding '[object HTMLDivElement]'), silently reset IN_PLACE to false, and return the unsanitized element unchanged with any XSS payloads intact.

Affected products

• CURE53 Dompurify: before 3.4.4 (fixed in 3.4.4)

Published 2026-07-23. Last modified 2026-07-28.