Package Instance

CKEditor4 low-risk cross-site scripting (XSS) vulnerability linked to potential domain takeover
### Affected Packages

The issue impacts only editor instances with enabled [version notifications](https://ckeditor.com/docs/ckeditor4/latest/api/CKEDITOR_config.html#cfg-versionCheck).

Please note that this feature is disabled by default in all CKEditor 4 LTS versions. Therefore, if you use CKEditor 4 LTS, it is highly unlikely that you are affected by this vulnerability. If you are unsure, please [contact us](mailto:security@cksource.com).

### Impact

A theoretical vulnerability has been identified in CKEditor 4.22 (and above). In a highly unlikely scenario where an attacker gains control over the https://cke4.ckeditor.com domain, they could potentially execute an attack on CKEditor 4 instances. Although the vulnerability is purely hypothetical, we have addressed it in CKEditor 4.25.0-lts to ensure compliance with security best practices.

### Patches

The issue has been recognized and patched. The fix is available in version 4.25.0-lts.

### For More Information

If you have any questions or comments about this advisory, please email us at [security@cksource.com](mailto:security@cksource.com).

Cross-site Scripting
ckeditor is an open source WYSIWYG HTML editor with rich content support. A vulnerability has been discovered in the clipboard Widget plugin if used alongside the undo feature. The vulnerability allows a user to abuse undo functionality using malformed widget HTML, which could result in executing JavaScript code. It affects all users using the CKEditor 4 plugins listed above at The problem has been recognized and patched. The fix will be available

Cross-site scripting (XSS) in the CKEditor 5 real-time collaboration package
### Impact
During a recent internal audit, we identified a Cross-Site Scripting (XSS) vulnerability in the CKEditor 5 real-time collaboration package. This vulnerability can lead to unauthorized JavaScript code execution and affects user markers, which represent users' positions within the document.

This vulnerability affects only installations with [Real-time collaborative editing](https://ckeditor.com/docs/ckeditor5/latest/features/collaboration/real-time-collaboration/real-time-collaboration.html) enabled.

### Patches
The problem has been recognized and patched. The fix will be available in version 44.2.1 (and above).

### For more information
Email us at [security@cksource.com](mailto:security@cksource.com) if you have any questions or comments about this advisory.

Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
CKEditor4 is an open source WYSIWYG HTML editor. The vulnerability allowed to inject malformed comments HTML bypassing content sanitization, which could result in executing JavaScript code. It affects all users using the CKEditor 4 at The problem has been recognized and patched.

Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
CKEditor4 is an open source WYSIWYG HTML editor. The vulnerability allowed to inject malformed HTML bypassing content sanitization, which could result in executing JavaScript code.

CKEditor 4 ReDoS Vulnerability
It was possible to execute a ReDoS-type attack inside CKEditor 4 before 4.16 by persuading a victim to paste crafted text into the Styles input of specific dialogs (in the Advanced Tab for Dialogs plugin).

Inclusion of Functionality from Untrusted Control Sphere in CKEditor 4
It was possible to execute a ReDoS-type attack inside CKEditor 4 before 4.16 by persuading a victim to paste crafted URL-like text into the editor, and then press Enter or Space (in the Autolink plugin).

Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
CKEditor4 is an open source what-you-see-is-what-you-get HTML editor. A cross-site scripting vulnerability has been discovered affecting Iframe Dialog and Media Embed packages. The vulnerability may trigger a JavaScript code after fulfilling special conditions: using one of the affected packages on a web page with missing proper Content Security Policy configuration; initializing the editor on an element and using an element other than `<textarea>` as a base; and destroying the editor instance. This vulnerability might affect a small percentage of integrators that depend on dynamic editor initialization/destroy mechanism. A fix is available in CKEditor4 version 4.21.0. In some rare cases, a security fix may be considered a breaking change. Starting from version 4.21.0, the Iframe Dialog plugin applies the `sandbox` attribute by default, which restricts JavaScript code execution in the iframe element. To change this behavior, configure the `config.iframe_attributes` option. Also starting from version 4.21.0, the Media Embed plugin regenerates the entire content of the embed widget by default. To change this behavior, configure the `config.embed_keepOriginalContent` option. Those who choose to enable either of the more permissive options or who cannot upgrade to a patched version should properly configure Content Security Policy to avoid any potential security issues that may arise from embedding iframe elements on their web page.

Cross-site Scripting
CKEditor allows user-assisted XSS involving a source-mode paste.