Fortis for WooCommerce <= 1.2.0 - Missing Authorization to Unauthenticated Arbitrary Order Status Update to Paid via 'wc-api' Endpoint

The Fortis for WooCommerce plugin for WordPress is vulnerable to authorization bypass due to an inverted nonce check in the 'check_fortis_notify_response' function in all versions up to, and including, 1.2.0. This makes it possible for unauthenticated attackers to update arbitrary WooCommerce order statuses to paid/processing/completed, effectively allowing them to mark orders as paid without payment.