WordPress is an open publishing platform for the Web. It's possible for a file of a type other than a zip file to be submitted as a new plugin by an administrative user on the Plugins -> Add New -> Upload Plugin screen in WordPress. If FTP credentials are requested for installation (in order to move the file into place outside of the `uploads` directory) then the uploaded file remains temporary available in the Media Library despite it not being allowed. If the `DISALLOW_FILE_EDIT` constant is set to `true` on the site _and_ FTP credentials are required when uploading a new theme or plugin, then this technically allows an RCE when the user would otherwise have no means of executing arbitrary PHP code. This issue _only_ affects Administrator level users on single site installations, and Sup