Theme Editor lets forged administrator requests alter child-theme CSS
Theme Editor through 3.1 does not validate a nonce in the ms_update AJAX action. An unauthenticated attacker can prepare a forged request containing attacker-controlled child-theme CSS; if a logged-in Administrator is induced to submit it, the action modifies the site's theme styles.
- Component
- Theme Editor
- Plugin slug
theme-editor- Affected
- <= 3.1
- Safe version
- See mitigation notes
- Published
- Aug 01, 2026
This CVE was published Aug 01, 2026 and is one of 6 known issues for this plugin.
Update, patch or deactivate.
No fixed public release is identified for Theme Editor through 3.1. Restrict Administrator browsing while logged in or deactivate the plugin when the site's risk profile warrants it until a corrected release is available. Review child-theme CSS and ms_update requests for unauthorized changes, and restore altered styles from a trusted copy.
No confirmed safe version is listed. Consider a vendor-supported patch or temporarily restricting the affected functionality while you assess the risk.
Deactivate only when warranted by your risk profile, or when advised by your hosting provider in the limited circumstances where the vulnerability cannot otherwise be mitigated. If you’re unsure which action is appropriate, contact Fused or your hosting provider for guidance.
Technical description
The Theme Editor plugin for WordPress is vulnerable to Cross-Site Request Forgery in all versions up to, and including, 3.1. This is due to missing nonce validation on the ms_update AJAX action. This makes it possible for unauthenticated attackers to modify child theme CSS styles via a forged request granted they can trick an administrator into performing an action such as clicking on a link.
CVE / CNA vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N