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.
Exploitability
AV:NAC:LPR:NUI:RScope
S:UImpact
C:NI:LA:N4.3/CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:NAuthentication