The changelog for the latest version of Theme Editor is “Security issues fixes”. Looking at the changes made in that we found that various functions in the plugin had security checks added. In most cases a capabilities check was added, to limit what users could access them. In some there was also previously a missing nonce check to prevent cross-site request forgery (CSRF), so anyone logged in to WordPress could previously access them. Among the things that previously anyone logged in to WordPress could do is to view the contents of arbitrary files and upload arbitrary files, both of which are things that hackers are highly likely to exploit when not requiring authentication, so they would be of concern even when requiring authentication.

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This post provides insights on a vulnerability in the WordPress plugin Theme Editor not discovered by us, where the discoverer hadn't provided the details needed for us to confirm the vulnerability while we were adding it to the data set for our service, so the rest of its contents are limited to subscribers of our service.

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