In a statement on Monday (Tuesday Australian time), the firm said that those who had made purchases from its American, German, Dutch, Belgian and French sites were not affected.
An OppoSuits spokesperson told iTWire that 7000 customers whose data may have been compromised had been contacted on Monday. The rogue software was discovered on 22 November.
While the company did not detail the malware planted, it appears to have been another attack by one of the Magecart groups that inject code into payment pages on shopping sites and steal credit card details.
In the statement, OppoSuits said the information which could have been compromised included names, addresses, email addresses, telephone numbers and credit card details.
"We have been working with appropriate local and international authorities, security experts, and payment service providers to understand how the data was compromised, and have taken security measures as described in the next bullet point," OppoSuits said.
"Our security experts have removed the malignant software from the affected websites upon discovery. The check-out page on all our websites is now diverted to the Hosted Payment Page of our payment service provider Adyen where an extra layer of security is added.
"Our server files dating back to the first day of the breach have been secured and we have initiated an in-depth security audit."