In what seems to be a more alarming development, a customer support portal for firms which use Oracle's Micros point-of-sale credit card payment system has also been breached, the report said.
The company has asked users of the system to change their passwords. It has also acknowledged that it had detected and addresses malicious code in certain legacy Micros systems.
Oracle purchased Micros Systems, a manufacturer of online cash registers, for US$5.3 billion in 2014. A total of 330,000 customer sites use the software.
According to security experts quoted in the report, the Micros customer support portal had been communicating with a server known to be used by the Carbanak Gang.
This gang is said to have stolen more than US$1 billion from banks, retailers and hospitality firms over the last few years.
Many point of sale systems which collect credit card details have been targeted in the recent past. Target was hit in 2013, Home Depot followed, and more recently Hilton Hotels, Starwood Hotels and Resorts, Mandarin Oriental and Trump Collection have all taken a hit, according to the Financial Times.