GHSA-fq6h-4g8v-qqvm
MEDIUMCKEditor4 Cross-site Scripting vulnerability caused by incorrect CDATA detection
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
Blast Radius
ckeditor4🐘ckeditor/ckeditorReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects npm, Packagist packages — download data is not available via public APIs for these ecosystems.
Description
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-lts |
| 🐘Packagist | ckeditor/ckeditor | all versions | 4.24.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for ckeditor4. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
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
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-fq6h-4g8v-qqvm is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-fq6h-4g8v-qqvm. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-fq6h-4g8v-qqvm in your dependencies?
O3 detects GHSA-fq6h-4g8v-qqvm across npm, Packagist dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.