CKEditor4 Cross-site Scripting vulnerability caused by incorrect CDATA detection

Affected packages

The vulnerability has been discovered in the core HTML parsing module and may affect all editor instances that:

• Enabled full-page editing mode,
• or enabled CDATA elements in Advanced Content Filtering configuration (defaults to script and style elements).

Impact

A potential vulnerability has been discovered in CKEditor 4 HTML processing core module. The vulnerability allowed to inject malformed HTML content bypassing Advanced Content Filtering mechanism, which could result in executing JavaScript code. An attacker could abuse faulty CDATA content detection and use it to prepare an intentional attack on the editor. It affects all users using the CKEditor 4 at version < 4.24.0-lts.

Patches

The problem has been recognized and patched. The fix will be available in version 4.24.0-lts.

For more information

Email us at [email protected] if you have any questions or comments about this advisory.

Acknowledgements

The CKEditor 4 team would like to thank Michal Frýba from ALEF NULA for recognizing and reporting this vulnerability.