GHSA-438c-3975-5x3f
MEDIUMTinyMCE Cross-Site Scripting (XSS) vulnerability in handling iframes
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 TinyMCE’s content insertion code. This allowed iframe elements containing malicious code to execute when inserted into the editor. These iframe elements are restricted in their permissions by same-origin browser protections, but could still trigger operations such as downloading of malicious assets.
Fix
TinyMCE 6.8.1 introduced a new sandbox_iframes boolean option which adds the sandbox="" attribute to every iframe element by default when enabled. This will prevent cross-origin, and in special cases same-origin, XSS by embedded resources in iframe elements. From TinyMCE 7.0.0 onwards the default value of this option is true.
In TinyMCE 7.0.0 a new sandbox_iframes_exclusions option was also added, allowing a list of domains to be specified that should be excluded from having the sandbox="" attribute applied when the sandbox_iframes option is enabled. By default, this option is set to an array of domains that are provided in embed code by popular websites. To sandbox iframe elements from every domain, set this option to [].
Workarounds
The HTTP Content-Security-Policy (CSP) frame-src or object-src can be configured to restrict or block the loading of unauthorized URLS. Refer to the TinyMCE Content Security Policy Guide.
References
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | tinymce | all versions | 6.8.1 |
| .NETNuGet | TinyMCE | all versions | 6.8.1 |
| 🐘Packagist | tinymce/tinymce | all versions | 6.8.1 |
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 6.8.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-438c-3975-5x3f 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-438c-3975-5x3f 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-438c-3975-5x3f. 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-438c-3975-5x3f in your dependencies?
O3 detects GHSA-438c-3975-5x3f 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.