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.
Credits
Identified by Cantina’s Apex (https://www.cantina.security).
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.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
Remediation advice
Kodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.
Frequently Asked Questions
- What is GHSA-CJMM-F4JC-QW8R? GHSA-CJMM-F4JC-QW8R is a medium-severity security vulnerability in dompurify (npm), affecting versions <= 3.3.1. It is fixed in 3.3.2.
- Which versions of dompurify are affected by GHSA-CJMM-F4JC-QW8R? dompurify (npm) versions <= 3.3.1 is affected.
- Is there a fix for GHSA-CJMM-F4JC-QW8R? Yes. GHSA-CJMM-F4JC-QW8R is fixed in 3.3.2. Upgrade to this version or later.
- Is GHSA-CJMM-F4JC-QW8R exploitable, and should I be worried? Whether GHSA-CJMM-F4JC-QW8R is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether GHSA-CJMM-F4JC-QW8R is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix GHSA-CJMM-F4JC-QW8R? Upgrade
dompurifyto 3.3.2 or later.