The Klarna for WooCommerce plugin for WordPress is vulnerable to authorization bypass in all versions up to, and including, 4.13.3 This is due to the plugin not properly verifying that a user is authorized to perform an action. This makes it possible for unauthenticated attackers to access any order's secret order_key and full billing and shipping PII — including first name, last name, email address, phone number, street address, postcode, city, region, and country — emitted inline as the klarna_payments_params JavaScript variable, enabling full store-wide order enumeration. Because WooCommerce order IDs are sequential integers and no order_key or authenticated session is required, every order in the store can be trivially enumerated with sequential GET requests to the order-pay endpoint.