Cross-site scripting vulnerability in TinyMCEGHSA-5h9g-x5rv-25wg
MEDIUMGHSA-5h9g-x5rv-25wg is a medium-severity (CVSS 6.1) Cross-site Scripting (XSS) vulnerability in tinymce. 2 public exploit references exist, so weaponization risk is real. A fix is available for tinymce — 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-5h9g-x5rv-25wg.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
GHSA-5h9g-x5rv-25wg by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 385,987 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
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.
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 | 5.9.0npm install tinymce@5.9.0 |
| .NETNuGet | TinyMCE | all versions | 5.9.0dotnet add package TinyMCE --version 5.9.0 |
| 🐘Packagist | tinymce/tinymce | all versions | 5.9.0composer require tinymce/tinymce:^5.9.0 |
Affected Products
tinymcetinyResearch 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, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
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
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-5h9g-x5rv-25wg in your dependencies?
Find it across npm, NuGet, Packagist, including transitive dependencies.