DOMPurify USE_PROFILES prototype pollution allows event handlers
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).
Affected software
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| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| npm package | dompurify | < 3.3.2 | 3.3.2 |
References
- CVSS vector
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:L/VA:N/SC:L/SI:L/SA:N- Weakness (CWE)
CWE-1321- Platform
- npm
- Package
dompurify- Disclosed
- 03.04.2026
- Updated
- 11.10.2026 10:22
Sources and licenses
OSV / GitHub Advisory Database - GHSA-cj63-jhhr-wcxv - CC BY 4.0
Vulnerability history: dompurify
All published vulnerabilities of this package (npm package), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 30
- First → latest
- 08.2020 10.2026
- Without a fix
- 1
- Exploited in attacks
- 0
Severity breakdown
- Critical 2
- High 3
- Medium 19
- Low 6
Disclosures per year
- 2020: 3
- 2021: 0
- 2022: 0
- 2023: 1
- 2024: 3
- 2025: 1
- 2026: 22
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DOMPurify USE_PROFILES prototype pollution allows event handlers this entry
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