medium6.9
CVE-2026-41238
DOMPurify is a DOM-only cross-site scripting sanitizer for HTML, MathML, and SVG.
Impact
DOMPurify is a DOM-only cross-site scripting sanitizer for HTML, MathML, and SVG. Versions 3.0.1 through 3.3.3 are vulnerable to a prototype pollution-based XSS bypass. When an application uses `DOMPurify.sanitize()` with the default configuration (no `CUSTOM_ELEMENT_HANDLING` option), a prior prototype pollution gadget can inject permissive `tagNameCheck` and `attributeNameCheck` regex values into `Object.prototype`, causing DOMPurify to allow arbitrary custom elements with arbitrary attributes — including event handlers — through sanitization. Version 3.4.0 fixes the issue.
Affected packages
| Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|
| npm | dompurify | >= 3.0.1, < 3.4.0 | 3.4.0 |