Printcart WooCommerce plugin: unauthenticated file upload leads to remote code execution

The Printcart Store – Web to Print Product Designer for WooCommerce plugin for WordPress is vulnerable to Arbitrary File Upload in all versions up to, and including, 2.13.2. This is due to the nbu_crop_image AJAX handler accepting a user-supplied url parameter that Nbdesigner_IO::convert_url_to_path() concatenates onto the uploads base directory without normalizing or stripping ../ sequences, and then deriving both the output directory and output file extension via pathinfo() from the same attacker-controlled path — with no stripImage() call before writeImage() is invoked. This makes it possible for unauthenticated attackers to write attacker-controlled PHP content to arbitrary locations outside the uploads directory, resulting in remote code execution when the written file is subsequently requested. This vulnerability is only exploitable when the nbdesigner_upload_popup_style site option is set to a (Advanced Upload Popup), which causes the handler to be registered for unauthenticated requests; however, the required save-design nonce is printed on the fully public frontend page, making it trivially obtainable by any anonymous visitor once that configuration is active.