Description
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
References3
- github.com/cure53/DOMPurify/security/advisories/GHSA-4w3q-35jp-… ExploitThird Party Advisory
- github.com/cure53/DOMPurify/security/advisories/GHSA-4w3q-35jp-… ExploitThird Party Advisory
- www.vulncheck.com/advisories/dompurify-before-cross-site-script… Third Party Advisory
Metrics
- CVSS 3.1
-
4.7
MEDIUM
Score source: CNA
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:L/I:L/A:N - CVSS 4.0
-
2.3
LOW
Score source: CNA
CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X - EPSS — exploit probability
- 0% percentile: 19 · as of 14 November 2026
- CWE
- CWE-754
Could this be exploited in your environment?
A patch closes the known hole. A penetration test shows what an attacker can still reach — with proof.