No-PIN attack
A 2010 man-in-the-middle attack that made an EMV terminal accept any PIN at all with a stolen card.
Steven Murdoch, Saar Drimer, Ross Anderson and Mike Bond at Cambridge built a rig out of a fake card, a thin cable, an FPGA board and a laptop. It sat between the genuine card and the terminal and passed everything through except one command: when the terminal asked the card to check the PIN, the rig answered "correct" on its own. The card never saw the question and assumed the purchase was being signed for. The terminal believed the PIN had been verified and printed as much on the receipt.
The flaw was that the PIN-verify response wasn't authenticated, and issuers didn't compare what the card actually reported with what the terminal claimed. The paper "Chip and PIN is Broken" and a BBC Newsnight segment in February 2010 made it awkward for British banks to keep insisting that a PIN transaction proved the customer guilty.