CVE-2024-21911

Cross-site scripting vulnerability in TinyMCE

editor.parser.addNodeFilter('iframe,object,embed', function(nodes) {
  nodes.forEach(function(node) {
    if (node.attributes) {
      node.attributes.forEach(function(attr) {
        var name = attr.name;
        var value = attr.value;
        // Sanitize the attribute value here or remove it entirely
        var sanitizedValue = ...;
        node.attr(name, santizedValue);
      });
    }
  });
});

invalid_elements: 'iframe,object,embed'

A cross-site scripting (XSS) vulnerability was discovered in the URL sanitization logic of the core parser. The vulnerability allowed arbitrary JavaScript execution when inserting a specially crafted piece of content into the editor using the clipboard or APIs. This impacts all users who are using TinyMCE 5.5.1 or lower.

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.

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This vulnerability has been patched in TinyMCE 5.6.0 by improved URL sanitization logic.

1. What is CVE-2024-21911? CVE-2024-21911 is a medium-severity cross-site scripting (XSS) vulnerability in tinymce (npm), affecting versions < 5.6.0. It is fixed in 5.6.0. Untrusted input is rendered as active markup in a victim's browser, which can run script in their session.
2. Which packages are affected by CVE-2024-21911?
   • tinymce (npm) (versions < 5.6.0)
   • TinyMCE (nuget) (versions < 5.6.0)
   • tinymce/tinymce (composer) (versions < 5.6.0)
3. Is there a fix for CVE-2024-21911? Yes. CVE-2024-21911 is fixed in 5.6.0. Upgrade to this version or later.
4. Is CVE-2024-21911 exploitable, and should I be worried? Whether CVE-2024-21911 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
5. What actually determines whether CVE-2024-21911 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.
6. How do I fix CVE-2024-21911?
   • Upgrade tinymce to 5.6.0 or later
   • Upgrade TinyMCE to 5.6.0 or later
   • Upgrade tinymce/tinymce to 5.6.0 or later

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