Hackers obtained the credit card details of some 380,000 British Airways travelers during a two-week data breach this summer that leaves the customers vulnerable to financial fraud. Enough data was stolen to allow criminals to use credit card information for illicit purposes, and that police are investigating.

British Airways assured customers that it would reimburse them for losses directly because of the breach but advised them to contact their credit card suppliers if they made a booking or change to their booking through BA’s website or mobile app between 22:58 BST on Aug. 21 (5.58 p.m. Eastern Time) and 21:45 BST (4.45 p.m. ET) on Sept. 5.

The hack once again puts the spotlight on the strength of the IT systems at major companies as they expand their digital services.