The Kliken: Ads + Pixel for Meta WordPress plugin before 1.2.3 does not verify that a visitor...

The Kliken: Ads + Pixel for Meta WordPress plugin before 1.2.3 does not verify that a visitor holds an order's key before outputting that order's details on the order confirmation page, allowing unauthenticated users to retrieve the billing location, purchased products and totals of other customers' orders by enumerating order IDs.