TinyMCE mXSS vulnerability in undo/redo, getContent API, resetContent API, and Autosave plugin
Impact
A mutation cross-site scripting (mXSS) vulnerability was discovered in TinyMCE’s core undo and redo functionality. When a carefully-crafted HTML snippet passes the XSS sanitisation layer, it is manipulated as a string by internal trimming functions before being stored in the undo stack. If the HTML snippet is restored from the undo stack, the combination of the string manipulation and reparative parsing by either the browser's native DOMParser API (TinyMCE 6) or the SaxParser API (TinyMCE 5) mutates the HTML maliciously, allowing an XSS payload to be executed. This vulnerability also impacts these related TinyMCE APIs and plugins:
Patches
This vulnerability has been patched in TinyMCE 5.10.8 and TinyMCE 6.7.1 by ensuring HTML is trimmed using node-level manipulation instead of string manipulation.
Fix
To avoid this vulnerability:
- Upgrade to TinyMCE 5.10.8 or higher for TinyMCE 5.x.
- Upgrade to TinyMCE 6.7.1 or higher for TinyMCE 6.x.
Acknowledgements
Tiny Technologies would like to thank Masato Kinugawa of Cure53 for discovering this vulnerability.
References
For more information
If you have any questions or comments about this advisory:
- Email us at infosec@tiny.cloud
- Open an issue in the TinyMCE repo
Affected software
Click a technology to see all vulnerabilities affecting it.
| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| Composer package | tinymce/tinymce | >= 6.0.0, < 6.7.1, < 5.10.8 | 6.7.1, 5.10.8 |
| npm package | tinymce | >= 6.0.0, < 6.7.1, < 5.10.8 | 6.7.1, 5.10.8 |
| .NET (NuGet) | TinyMCE | >= 6.0.0, < 6.7.1, < 5.10.8 | 6.7.1, 5.10.8 |
References
- https://github.com/tinymce/tinymce/security/advisories/GHSA-v65r-p3vv-jjfv
- https://nvd.nist.gov/vuln/detail/CVE-2023-45818
- https://github.com/tinymce/tinymce
- https://researchgate.net/publication/266654651_mXSS_attacks_Attacking_well-secured_web-applications_by_using_innerHTML_mutations
- https://tiny.cloud/docs/release-notes/release-notes5108/#securityfixes
- https://tiny.cloud/docs/tinymce/6/6.7.1-release-notes/#security-fixes
- https://www.tiny.cloud/docs/api/tinymce.html/tinymce.html.saxparser
- CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N- Weakness (CWE)
CWE-79- Platform
- Composer, npm, .NET (NuGet)
- Package
tinymce/tinymce, tinymce, TinyMCE- Disclosed
- 19.10.2023
- Updated
- 11.10.2026 11:23
Sources and licenses
OSV / GitHub Advisory Database - GHSA-v65r-p3vv-jjfv - CC BY 4.0
Vulnerability history: TinyMCE
All published vulnerabilities of this package (.NET (NuGet)), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 15
- First → latest
- 01.2021 06.2026
- Without a fix
- 0
- Exploited in attacks
- 0
Severity breakdown
- High 4
- Medium 11
Disclosures per year
- 2021: 3
- 2022: 1
- 2023: 3
- 2024: 4
- 2025: 0
- 2026: 4
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TinyMCE mXSS vulnerability in undo/redo, getContent API, resetContent API, and Autosave plugin this entry
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