PayHere Payment Gateway Plugin for WooCommerce <= 2.3.9 - Missing Authorization to Unauthenticated Order Status Modification

The PayHere Payment Gateway Plugin for WooCommerce plugin for WordPress is vulnerable to unauthorized modification of data due to an improper validation logic in the check_payhere_response function in all versions up to, and including, 2.3.9. This makes it possible for unauthenticated attackers to change the status of pending WooCommerce orders to paid/completed/on hold.