The WPFunnels WordPress plugin before 3.13.0 does not verify that the product requested through a checkout order bump is the product that bump's discount was configured for, allowing unauthenticated users to obtain any purchasable product at a discount intended for a different one, with the reduced price carried through to the total of the order they place.
https://wpscan.com/vulnerability/fb49c59a-f79f-495c-a23e-0e1629cfa53e/