For the first time, breached processor Global Payments disclosed on Tuesday that a number of card brands have removed the company from their approved list of Payment Card Industry (PCI)-compliant service providers.
However, the US-based firm continues to process transactions for all of the major card brands as it seeks rejoin those lists, it said in an update.
Global Payments stands by its initial estimate that fewer than 1.5 million cards were impacted by the breach. However, it declined to provide any further details or a timeline of the attack.
"We identified and self-reported the incident in early March, and we will continue to provide information to the appropriate parties as revealed by the investigation," the company said.
A Visa spokesman on Wednesday said it has asked Global Payments to re-validate its compliance to PCI by using a qualified security assessor, or QSA. Retailers that use the company's services will not be liable for penalties during that time.
A MasterCard spokesman did not respond to a request for comment.