The principle of credit card swiping is: after the merchant swipes the card, the user enters the password and the data is submitted to the bank. After the bank receives the confirmation, it will return it to the merchant and then print a small receipt for you to sign. If the merchant fails to print out the receipt due to power failure and other reasons, but you have entered the password and confirmed the transaction, the bank will deduct the money. If you swipe your card again, the bank will deduct it once and record it twice. However, because the data of the first transaction is not returned to the bank, under normal circumstances, the bank will correct the first credit card transaction within 24 hours.

But if your password is leaked, that's another matter.