Cross-site scripting vulnerability in TinyMCE

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

6.1 · CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

EPSS

• CVE-2024-21908: 1.07% estimated exploitation activity in the next 30 days; percentile 64.79 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

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 BeforeSetContent event (see below) Example: Manually sanitize content Acknowledgements Tiny Technologies would like to thank William Bowling for discovering this vulnerability. References…

Published by the source

22 Oct 2021, 16:24 UTC

Last modified by the source

8 Jul 2026, 06:52 UTC

Source last checked

26 Oct 2026, 12:30 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-5h9g-x5rv-25wg

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-5h9g-x5rv-25wg

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# Patch Next advisory brief: CVE-2024-21908

Advisory: Cross-site scripting vulnerability in TinyMCE
IDs: CVE-2024-21908, GHSA-5h9g-x5rv-25wg
Record: https://patchnext.com/advisories/cve-2024-21908 (revision 2, source checked 26 Oct 2026, 12:30 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.1)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: tinymce 5.9.0; tinymce/tinymce 5.9.0; tinymce 5.9.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- NuGet tinymce: affected < 5.9.0; fixed in 5.9.0
- Packagist tinymce/tinymce: affected < 5.9.0; fixed in 5.9.0
- npm tinymce: affected < 5.9.0; fixed in 5.9.0

## Suggested inspection (read-only)
- NuGet tinymce: check the installed version with your package manager.
- Packagist tinymce/tinymce: check the installed version with your package manager.
- `npm ls tinymce --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on tinymce, tinymce/tinymce.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-5h9g-x5rv-25wg (OSV record GHSA-5h9g-x5rv-25wg lists affected ranges: npm tinymce >=0 =0 =0 <5.9.0 (fixed))
- Verified: https://github.com/advisories/GHSA-5h9g-x5rv-25wg (GitHub-reviewed advisory GHSA-5h9g-x5rv-25wg lists affected ranges: npm tinymce >=0 =0 =0 <5.9.0)

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