DOMPurify ADD_ATTR predicate skips URI validation
Summary
DOMPurify allows ADD_ATTR to be provided as a predicate function via EXTRA_ELEMENT_HANDLING.attributeCheck. When the predicate returns true, _isValidAttribute short-circuits the attribute check before URI-safe validation runs. An attacker who supplies a predicate that accepts specific attribute/tag combinations can then sanitize input such as <a href="javascript:alert(document.domain)"> and have the javascript: URL survive, because URI validation is skipped for that attribute while other checks still pass. The provided PoC accepts href for anchors and then triggers a click inside an iframe, showing that the sanitized payload executes despite the protocol bypass.
Impact
Predicate-based allowlisting bypasses DOMPurify's URI validation, allowing unsafe protocols such as javascript: to reach the DOM and execute whenever the link is activated, resulting in DOM-based XSS.
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:N/VA:N/SC:L/SI:L/SA:N- Weakness (CWE)
CWE-183- Platform
- npm
- Package
dompurify- Disclosed
- 03.04.2026
- Updated
- 11.10.2026 10:22
Sources and licenses
OSV / GitHub Advisory Database - GHSA-cjmm-f4jc-qw8r - 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 ADD_ATTR predicate skips URI validation this entry
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