A UK-based hacker stole 7.4m worth of virtual poker chips after gaming firm Zynga failed to monitor key database tables.
Ashley Mitchell, already under a suspended sentence for hacking into computers at a local council, will face a lengthy prison sentence for the theft.
At Exeter Crown Court, Ashley Mitchell pleaded guilty to five charges brought under the Computer Misuse Act and the Proceeds from Crime Act.
He is to be held in custody until a date is fixed for sentencing.
Mitchell was caught in a sting operation after Zynga was alerted to the theft by the volume of chips going missing, according to the BBC.
Security experts said the “chips” were merely values in a database. Mitchell simply manipulated these values once he had access to administration controls.
Monitoring the tables would have enabled Zynga to track access to that table and trigger alerts of abnormal and suspicious behaviour, they said.