WooCommerce Upload Files < 59.4 - Unauthenticated Arbitrary File Upload

The WooCommerce Upload Files WordPress plugin before 59.4 ran a single sanitization pass to remove blocked extensions such as .php. It was possible to bypass this and upload a file with a PHP extension by embedding a "blocked" extension within another "blocked" extension in the "wcuf_file_name" parameter. It was also possible to perform a double extension attack and upload files to a different location via path traversal using the "wcuf_current_upload_session_id" parameter.