CVE-2024-21911

### Impact 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. ### Patches This vulnerability has been patched in TinyMCE 5.6.0 by improved URL sanitization logic. ### Workarounds To work around this vulnerability, either: - Upgrade to TinyMCE 5.6.0 or higher - Manually sanitize `iframe`, `object` and `embed` URL attributes using a [TinyMCE node filter](https://www.tiny.cloud/docs/api/tinymce.html/tinymce.html.domparser/#addnodefilter). - Disable `iframe`, `object`, and `embed` elements in your content using the [invalid_elements](https://www.tiny.cloud/docs/configure/content-filtering/#invalid_elements) setting. #### Example: Sanitizing using a node filter ```js 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); }); } }); }); ``` #### Example: Using invalid_elements ```js invalid_elements: 'iframe,object,embed' ``` ### Acknowledgements Tiny Technologies would like to thank Aaron Bishop at SecurityMetrics for discovering this vulnerability. ### References https://www.tiny.cloud/docs/release-notes/release-notes56/#securityfixes ### For more information If you have any questions or comments about this advisory: * Open an issue in the [TinyMCE repo](https://github.com/tinymce/tinymce/issues) * Email us at [infosec@tiny.cloud](mailto:infosec@tiny.cloud)