CVE-2023-45818: TinyMCE is an open source rich text editor. A mutation cross-site scripting (mXSS) vulnerability was discovered in TinyMCE’s core undo and redo functi...

Description

TinyMCE is an open source rich text editor. 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](https://developer.mozilla.org/en-US/docs/Web/API/DOMParser) (TinyMCE 6) or the SaxParser API (TinyMCE 5) mutates the HTML maliciously, allowing an XSS payload to be executed. 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. Users are advised to upgrade. There are no known workarounds for this vulnerability.

Metrics

CVSS 3.1

6.1/10

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

EPSS Probability

0.62%

45.1th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Vendor	Product	Versions
Tiny	Tinymce	< 5.10.8
Tiny	Tinymce	>= 6.0.0, < 6.7.1

References

https://github.com/tinymce/tinymce/security/advisories/GHSA-v65r-p3vv-jjfvVendor Advisory
https://researchgate.net/publication/266654651_mXSS_attacks_Attacking_well-secured_web-applications_by_using_innerHTML_mutationsThird Party Advisory
https://tiny.cloud/docs/release-notes/release-notes5108/#securityfixesRelease Notes
https://tiny.cloud/docs/tinymce/6/6.7.1-release-notes/#security-fixesRelease Notes
https://www.tiny.cloud/docs/api/tinymce.html/tinymce.html.saxparser/Product
https://github.com/tinymce/tinymce/security/advisories/GHSA-v65r-p3vv-jjfvVendor Advisory
https://researchgate.net/publication/266654651_mXSS_attacks_Attacking_well-secured_web-applications_by_using_innerHTML_mutationsThird Party Advisory
https://tiny.cloud/docs/release-notes/release-notes5108/#securityfixesRelease Notes
https://tiny.cloud/docs/tinymce/6/6.7.1-release-notes/#security-fixesRelease Notes
https://www.tiny.cloud/docs/api/tinymce.html/tinymce.html.saxparser/Product

Timeline

Published: Oct 19, 2023
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2023-45818?

TinyMCE is an open source rich text editor. 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](https://developer.mozilla.org/en-US/docs/Web/API/DOMParser) (TinyMCE 6) or the SaxParser API (TinyMCE 5) mutates the HTML maliciously, allowing an XSS payload to be executed. 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. Users are advised to upgrade. There are no known workarounds for this vulnerability.

How severe is CVE-2023-45818?

CVE-2023-45818 has a CVSS score of 6.1/10 (MEDIUM severity). The EPSS model estimates a 0.62% probability of exploitation in the next 30 days.

How do I fix CVE-2023-45818?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.