Summary
Cross-Site Scripting in yui
Affected versions of yui are vulnerable to cross-site scripting in the uploader.swf and io.swf utilities, via script injection in the url.
Impact
Untrusted input is rendered as active markup in a victim's browser, which can run script in their session. Typical impact: session or credential theft, and actions taken as the user.
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
YUI has published their recommendation to fix this issue.
Their recommendation is to:
- Delete self-hosted copies of these files if you are not using them
- Use the Yahoo! CDN hosted files
- Use the patched files provided on the YUI Library here.
Frequently Asked Questions
- What is CVE-2013-4939? CVE-2013-4939 is a medium-severity cross-site scripting (XSS) vulnerability in yui (npm), affecting versions < 3.10.2. It is fixed in 3.10.3. Untrusted input is rendered as active markup in a victim's browser, which can run script in their session.
- Which versions of yui are affected by CVE-2013-4939? yui (npm) versions < 3.10.2 is affected.
- Is there a fix for CVE-2013-4939? Yes. CVE-2013-4939 is fixed in 3.10.3. Upgrade to this version or later.
- Is CVE-2013-4939 exploitable, and should I be worried? Whether CVE-2013-4939 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 CVE-2013-4939 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 CVE-2013-4939? Upgrade
yuito 3.10.3 or later.