Eventin <= 4.1.22 - Missing Authorization to Unauthenticated Arbitrary Order Creation and Status Manipulation via 'status' Parameter

The WP Event Solution (Eventin) plugin for WordPress is vulnerable to Missing Authorization in versions up to, and including, 4.1.22 via the create_item() handler for the /wp-json/eventin/v2/orders REST endpoint. The endpoint's create_item_permissions_check() function only verifies a wp_rest nonce (which is leaked to every visitor through the etn-public script's localized_data_obj on every frontend page) and accepts a user-supplied 'status' value in prepare_item_for_database() with no whitelist validation. This makes it possible for unauthenticated attackers to create etn-order posts with status='completed' that are counted as sold by etn_get_sold_tickets_by_event(); because the auto-cleanup wp_schedule_single_event() in create_item() only fires for status='pending' orders, the forged completed orders persist indefinitely and exhaust ticket inventory.