CVE-2026-28343: CKEditor: Cross-site scripting (XSS) in the HTML Support package
Impact A Cross-Site Scripting (XSS) vulnerability has been discovered in the General HTML Support feature. This vulnerability could be triggered by inserting specially crafted markup, leading to unauthorized JavaScript code execution, if the editor instance used an unsafe General HTML Support configuration.
This vulnerability affects only installations where the editor configuration meets the following criteria:
General HTML Support is enabled, General HTML Support configuration allows inserting unsafe markup (see Security section to learn more).
Patches The problem has been recognized and patched. The fix will be available in version 47.6.0 (and above).
Workarounds CKEditor 5 recommends configuring General HTML Support securely to ensure that unsafe content is not accepted. Please refer to the Security section for detailed guidance.
Credits CKEditor 5 would like to thank: - Emilio Kevin - Jeongwoo Lee, Younsoung Kim, Minseok Kim and Jinyeong Kim from ENKI Whitehat
for responsibly reporting this vulnerability.
For more information Email us at security@cksource.com if you have any questions or comments about this advisory.
Other sources
CKEditor 5 is a modern JavaScript rich-text editor with an MVC architecture. Prior to version 47.6.0, a cross-site scripting (XSS) vulnerability has been discovered in the General HTML Support feature. This vulnerability could be triggered by inserting specially crafted markup, leading to unauthorized JavaScript code execution, if the editor instance used an unsafe General HTML Support configuration. This issue has been patched in version 47.6.0.
— NVD
CKEditor 5 is a modern JavaScript rich-text editor with an MVC architecture. Starting in version 29.0.0 and prior to version 47.6.0, a cross-site scripting (XSS) vulnerability has been discovered in the General HTML Support feature. This vulnerability could be triggered by inserting specially crafted markup, leading to unauthorized JavaScript code execution, if the editor instance used an unsafe General HTML Support configuration. This issue has been patched in version 47.6.0.
— MITRE
Affected Software
Event History
Frequently Asked Questions
What is the severity of CVE-2026-28343?
CVE-2026-28343 is classified as a high severity vulnerability due to its potential for unauthorized JavaScript execution.
How do I fix CVE-2026-28343?
To fix CVE-2026-28343, update to version 47.6.0 or later of the affected CKEditor 5 packages.
What software is affected by CVE-2026-28343?
CVE-2026-28343 affects CKEditor 5 and @ckeditor/ckeditor5-html-support prior to version 47.6.0.
What type of vulnerability is CVE-2026-28343?
CVE-2026-28343 is a Cross-Site Scripting (XSS) vulnerability.
What can happen if CVE-2026-28343 is exploited?
If CVE-2026-28343 is exploited, it can lead to unauthorized execution of JavaScript in users' browsers.