The WP Duplicate plugin for WordPress is vulnerable to Missing Authorization leading to Arbitrary File Upload in all versions up to and including 1.1.8. This is due to a missing capability check on the `process_add_site()` AJAX action combined with path traversal in the file upload functionality. This makes it possible for authenticated (subscriber-level) attackers to set the internal `prod_key_random_id` option, which can then be used by an unauthenticated attacker to bypass authentication checks and write arbitrary files to the server via the `handle_upload_single_big_file()` function, ultimately leading to remote code execution.