Welcart e-Commerce < 2.11.33 - Unauthenticated Payment Bypass via Forged Settlement Callback

The Welcart e-Commerce WordPress plugin before 2.11.33 does not verify the authenticity of its convenience-store / bank-transfer settlement callback: an unauthenticated request can flip an order from unpaid to settled purely from an order number and a status flag, with no signature, amount, or origin check. Because these are pay-later methods, an attacker can mark their own unpaid order as settled and obtain fulfilment without paying.