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TinyMCE Cross-Site Scripting (XSS) vulnerability using through data-mce- prefixed src, href, style attributes

High severity GitHub Reviewed Published May 20, 2026 in tinymce/tinymce • Updated Jun 5, 2026

Package

nuget TinyMCE (NuGet)

Affected versions

< 5.11.1
>= 6.0.0, < 7.9.3
>= 8.0.0, < 8.5.1

Patched versions

5.11.1
7.9.3
8.5.1
npm tinymce (npm)
< 5.11.1
>= 6.0.0, < 7.9.3
>= 8.0.0, < 8.5.1
7.9.3
8.5.1
composer tinymce/tinymce (Composer)
< 5.11.1
>= 6.0.0, < 7.9.3
>= 8.0.0, < 8.5.1
7.9.3
8.5.1

Description

Impact

Stored XSS vulnerability via unsanitized data-mce-* attributes (data-mce-href, data-mce-src, data-mce-style). Allows attackers to inject malicious values that override safe attributes during serialization, bypassing validation.

Patches

Patched by stripping unsafe data-mce-* attributes during parsing. Users should upgrade to the latest patched versions (5 LTS, 7.x, 8.x).

Workarounds

No official workaround available.

Fix

To avoid this vulnerability:

Upgrade to TinyMCE 8.5.1 or higher.
Upgrade to TinyMCE 7.9.3 or higher.
Upgrade to TinyMCE 5.11.1 LTS or higher for TinyMCE 5.x (only available as part of commercial long-term support contract).

Acknowledgements

Tiny thanks Tadi Kadango (website) and Ivan Babenko for their help identifying this vulnerability.

References

@MitchC1999 MitchC1999 published to tinymce/tinymce May 20, 2026
Published by the National Vulnerability Database May 28, 2026
Published to the GitHub Advisory Database Jun 5, 2026
Reviewed Jun 5, 2026
Last updated Jun 5, 2026

Severity

High

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
Low
Privileges required
Low
User interaction
Required
Scope
Changed
Confidentiality
High
Integrity
High
Availability
None

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:N

EPSS score

Exploit Prediction Scoring System (EPSS)

This score estimates the probability of this vulnerability being exploited within the next 30 days. Data provided by FIRST.
(10th percentile)

Weaknesses

Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users. Learn more on MITRE.

CVE ID

CVE-2026-47759

GHSA ID

GHSA-q742-qvgc-gc2f

Source code

Credits

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