MediumGHSA-v65r-p3vv-jjfvCVE-2023-45818

TinyMCE mXSS vulnerability in undo/redo, getContent API, resetContent API, and Autosave plugin

Published 19 Oct 2023 · Updated 10 Sept 2026

Affected packages

tinymcenpm

Affected: >=6.0.0 <6.7.1
Fixed in: 6.7.1

Update to the fixed version for your release line, for example:npm install tinymce@6.7.1

tinymce/tinymceComposer

Affected: >=6.0.0 <6.7.1
Fixed in: 6.7.1

Update to the fixed version for your release line, for example:composer require tinymce/tinymce:^6.7.1

tinymcenpm

Affected: <5.10.8
Fixed in: 5.10.8

Update to the fixed version for your release line, for example:npm install tinymce@5.10.8

tinymce/tinymceComposer

Affected: <5.10.8
Fixed in: 5.10.8

Update to the fixed version for your release line, for example:composer require tinymce/tinymce:^5.10.8

Details

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

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References

Advisory data from OSV.dev (opens OSV.dev in a new tab), refreshed daily.