WooCommerce PayPal Pro plugin: unpaid orders can be marked as paid

WooCommerce PayPal Pro Payment Gateway plugin before 4.1.1 contains an unauthenticated payment bypass vulnerability that allows remote attackers to mark unpaid orders as paid by exploiting the pp_capture_order AJAX handler, which is gated only by a public checkout nonce and fails to properly validate the PayPal capture response status. Attackers can supply a valid _paypal_order_id to trigger payment_complete() without verifying the capture status or amount, causing the store to fulfill goods or services that were never paid for and resulting in direct financial loss to the merchant.