Kmart hacked, exposing customers' card numbers

There is no evidence that the breach has affected customers who have shopped online at kmart.com, the company said.

Kmart is working with a federal law enforcement authorities, its banking partners and IT security firms in an ongoing investigation, Sears said.

Kmart is one of many major retailers to have been breached this year. Home Depot said last month its payment systems had been breached, putting at least 56 million cards at risk.