The File Manager Pro plugin for WordPress is vulnerable to arbitrary backup file downloads and uploads due to missing file type validation via the 'mk_file_folder_manager_shortcode' ajax action in all versions up to, and including, 8.3.9. This makes it possible for unauthenticated attackers, if granted access to the File Manager by an administrator, to download and upload arbitrary backup files on the affected site's server which may make remote code execution possible.