If you've been to this fast food chain recently, better check your bank statement

Millions of restaurant customers may have been hacked.

There's been a massive cyberattack on Sonic Drive-In, the popular drive-up fast food chain from Oklahoma. 

But since the investigation into the incident is still in its early stages, it's not yet clear which stores – or how many – were impacted, the company tells security journalist Brian Krebs

KrebsonSecurity says Sonic was informed by its credit card processor of "unusual activity" last week, and that a "batch of 5 million cards" ended up on a dark web marketplace called Joker's Stash (though it's not clear if all those came from Sonic).

News of the hack led to Sonic's worst stock decline in almost two months, Bloomberg reports

This is the latest in a long series of fast-food cyberattacks. Earlier this year, hackers hit Chipotle's payment systems, and last year, Wendy's was the target. 

GoMN has reached out to the chain for comment. 

There are five Sonic locations in Minnesota: Bloomington, Columbia Heights, Elk River, St. Paul, and Savage.

The company, which was founded in 1959 in Shawnee, Oklahoma, now has more than 3,500 stores in 44 states. 

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