Declan Rice endured a nightmare return to West Ham as Arsenal were dumped out of the Carabao Cup in the fourth round following a 3-1 defeat.
Ben White headed an own goal past Aaron Ramsdale – playing his first club game since September – before Mohammed Kudus and Jarrod Bowen secured the win.
Martin Odegaard scored a consolation for Arsenal deep into stoppage time.
Rice, a £105 million signing for Arsenal from West Ham in the summer, came on as a second-half substitute.
But he could not stop his former club reaching the quarter-finals.
The Gunners’ 30-year wait to win the League Cup goes on, while West Ham are into the last eight for the third successive season.