Xendit Payment <= 6.0.2 - Missing Authorization to Unauthenticated Arbitrary Order Status Update to Paid

The Xendit Payment plugin for WordPress is vulnerable to unauthorized order status manipulation in all versions up to, and including, 6.0.2. This is due to the plugin exposing a publicly accessible WooCommerce API callback endpoint (`wc_xendit_callback`) that processes payment callbacks without any authentication or cryptographic verification that the requests originate from Xendit's payment gateway. This makes it possible for unauthenticated attackers to mark any WooCommerce order as paid by sending a crafted POST request to the callback URL with a JSON body containing an `external_id` matching the order ID pattern and a `status` of 'PAID' or 'SETTLED', granted they can enumerate order IDs (which are sequential integers). This leads to orders being fraudulently marked as completed without any actual payment, resulting in financial loss and inventory depletion.