Helloprint <= 2.1.2 - Missing Authorization to Unauthenticated Arbitrary Order Status Modification

The Helloprint plugin for WordPress is vulnerable to Missing Authorization in versions up to, and including, 2.1.2. This is due to the plugin registering a public REST API endpoint without implementing authorization checks to verify request authenticity. This makes it possible for unauthenticated attackers to arbitrarily modify WooCommerce order statuses via the /wp-json/helloprint/v1/complete_order_from_helloprint_callback endpoint by providing a valid order reference ID.