CKEditor4 Cross-site Scripting vulnerability caused by incorrect CDATA detectionGHSA-fq6h-4g8v-qqvm
MEDIUMFix: ckeditor/ckeditor4@8ed1a3cGHSA-fq6h-4g8v-qqvm is a medium-severity (CVSS 6.1) Cross-site Scripting (XSS) vulnerability in ckeditor4. A fix is available for ckeditor4 — see the affected versions and patch details below.
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for GHSA-fq6h-4g8v-qqvm.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
Where this sits among everything scored
Real-World Exposure
How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.
ckeditor4npmDescription
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
scriptandstyleelements).
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.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | ckeditor4 | all versions | 4.24.0-ltsnpm install ckeditor4@4.24.0-lts |
| 🐘Packagist | ckeditor/ckeditor | all versions | 4.24.0composer require ckeditor/ckeditor:^4.24.0 |
Affected Products
ckeditorckeditorDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for ckeditor4, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update ckeditor4 to 4.24.0-lts or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-fq6h-4g8v-qqvm is resolved across your whole dependency graph.
Workarounds
Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.
Frequently Asked Questions
Is GHSA-fq6h-4g8v-qqvm in your dependencies?
Find it across npm, Packagist, including transitive dependencies.