Jurgen Klopp’s side played two entirely different XIs in the first and second halves, and got off to a superb start when Darwin Nunez slotted the opening goal into the net with less than three minutes gone.
Liverpool handed debuts to new signings Domink Szoboszlai and Alexis Mac Allister but conceded when ex-Germany midfielder Lars Stindl crashed a stunning volley off the crossbar and in.
Karlsruher took the lead after the break when Stindl played a smart pass and found right-back Sebastian Jung, who hammered past Liverpool goalkeeper VítÄzslav Jaroš.
Liverpool equalised when Diogo Jota headed down for Cody Gakpo to swivel and slam home for 2-2.
In stoppage time, Jota received the ball from Gakpo and weaved his way through the Karlsruher defence before knocking the ball coolly into the net. Within a minute he had scored again — Mac Allister winning the ball and finding Jota to score again.