CVE-2024-45613 Overview
CKEditor 5 contains a Cross-Site Scripting (XSS) vulnerability [CWE-79] in its clipboard package. The flaw affects versions starting at 40.0.0 and prior to 43.1.1. An attacker who inserts malicious content into the editor can trigger unauthorized JavaScript execution when a user performs a specific interaction. Exploitation requires a narrow configuration: the Block Toolbar plugin must be enabled alongside either the General HTML Support plugin (configured to permit unsafe markup) or the HTML Embed plugin. CKEditor released a fix in version 43.1.1.
Critical Impact
Successful exploitation allows attacker-controlled JavaScript to execute in the context of the victim's browser session, enabling session theft, content manipulation, or pivoting to authenticated actions.
Affected Products
- CKEditor 5 versions 40.0.0 through 43.1.0
- Deployments with the Block Toolbar plugin enabled
- Installations with General HTML Support (permissive configuration) or HTML Embed plugin enabled
Discovery Timeline
- 2024-09-25 - CVE-2024-45613 published to the National Vulnerability Database
- 2026-06-17 - Last updated in NVD database
Technical Details for CVE-2024-45613
Vulnerability Analysis
The vulnerability resides in the CKEditor 5 clipboard package, which handles paste and drag-drop operations within the rich-text editor. When the Block Toolbar plugin is combined with plugins that accept raw or embedded HTML, the clipboard pipeline fails to consistently sanitize markup passed through a specific user-initiated flow. An attacker who can seed malicious content into the editor (for example, through shared documents, collaborative editing, or preloaded fields) can craft payloads that survive normalization and execute when the victim triggers the vulnerable action.
The attack requires user interaction and depends on a specific plugin configuration, which narrows the exploitable surface. Successful execution runs script in the browser's document context, giving the attacker access to cookies, DOM contents, and any privileged UI actions the victim can perform.
Root Cause
The root cause is insufficient neutralization of input during web page generation. The clipboard package trusts markup produced by cooperating plugins (General HTML Support in unsafe mode or HTML Embed) at points where additional sanitization is required before rendering. The Block Toolbar interaction reintroduces this untrusted markup into the editable region without stripping executable script constructs.
Attack Vector
The attack vector is network-based with required user interaction. An attacker first places malicious HTML into a data source that populates the editor, such as a stored document, comment field, or shared collaborative content. When a victim opens the document and performs the specific action that engages the Block Toolbar plugin against the malicious node, the payload executes JavaScript within the origin hosting CKEditor 5.
No verified public exploit code is available. See the GitHub Security Advisory GHSA-rgg8-g5x8-wr9v for the vendor's technical description.
Detection Methods for CVE-2024-45613
Indicators of Compromise
- Unexpected <script> tags, on* event handler attributes, or javascript: URIs stored in fields backed by CKEditor 5
- Outbound requests from editor pages to unfamiliar domains shortly after users open shared documents
- Browser console errors or Content Security Policy (CSP) violations originating from editor-rendered content
Detection Strategies
- Inventory web applications embedding CKEditor 5 and identify versions between 40.0.0 and 43.1.0
- Review CKEditor configuration to flag installations that enable the Block Toolbar plugin together with General HTML Support (unsafe markup) or HTML Embed
- Scan stored editor content for HTML patterns commonly used in XSS payloads, including inline event handlers and embedded script nodes
Monitoring Recommendations
- Enable and monitor CSP violation reporting for pages that render CKEditor content
- Log and alert on anomalous DOM mutations or script injections in editor host pages using browser telemetry
- Correlate authenticated session anomalies (unexpected API calls, privilege changes) with recent editor interactions
How to Mitigate CVE-2024-45613
Immediate Actions Required
- Upgrade CKEditor 5 to version 43.1.1 or later across all applications
- Audit editor plugin configurations and disable unnecessary plugins, especially unsafe General HTML Support and HTML Embed
- Enforce a strict Content Security Policy on pages that render editor output to limit inline script execution
Patch Information
The vendor fixed the issue in CKEditor 5 version 43.1.1. Release notes and the corresponding advisory are available in the CKEditor 5 v43.1.1 release and the GitHub Security Advisory GHSA-rgg8-g5x8-wr9v.
Workarounds
- Disable the Block Toolbar plugin in CKEditor 5 configurations that cannot be upgraded immediately
- Reconfigure General HTML Support to disallow unsafe markup, or remove the HTML Embed plugin
- Sanitize editor content server-side before storage and again before rendering to strip executable HTML
# Configuration example: upgrade CKEditor 5 to the patched release
npm install ckeditor5@^43.1.1
# Alternative: disable the Block Toolbar plugin in the editor config
# ClassicEditor.create(element, { removePlugins: ['BlockToolbar'] })
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
