GHSA-5h9g-x5rv-25wg
MEDIUMCross-site scripting vulnerability in TinyMCE
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
Weekly download volume for affected packages — a proxy for how broadly this vulnerability is deployed.
tinymcenpmDescription
Impact
A cross-site scripting (XSS) vulnerability was discovered in the schema validation logic of the core parser. The vulnerability allowed arbitrary JavaScript execution when inserting a specially crafted piece of content into the editor using the clipboard or editor APIs. This malicious content could then end up in content published outside the editor, if no server-side sanitization was performed. This impacts all users who are using TinyMCE 5.8.2 or lower.
Patches
This vulnerability has been patched in TinyMCE 5.9.0 by ensuring schema validation was still performed after unwrapping invalid elements.
Workarounds
To work around this vulnerability, either:
- Upgrade to TinyMCE 5.9.0 or higher
- Manually sanitize the content using the
BeforeSetContentevent (see below)
Example: Manually sanitize content
editor.on('BeforeSetContent', function(e) {
var sanitizedContent = ...; // Manually sanitize content here
e.content = sanitizedContent;
});
Acknowledgements
Tiny Technologies would like to thank William Bowling for discovering this vulnerability.
References
https://www.tiny.cloud/docs/release-notes/release-notes59/#securityfixes
For more information
If you have any questions or comments about this advisory:
- Email us at [email protected]
- Open an issue in the TinyMCE repo
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | tinymce | all versions | 5.9.0 |
| .NETNuGet | TinyMCE | all versions | 5.9.0 |
| 🐘Packagist | tinymce/tinymce | all versions | 5.9.0 |
Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for tinymce. 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 tinymce to 5.9.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-5h9g-x5rv-25wg 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-5h9g-x5rv-25wg 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-5h9g-x5rv-25wg. 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-5h9g-x5rv-25wg in your dependencies?
O3 detects GHSA-5h9g-x5rv-25wg across npm, NuGet, Packagist dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.