A reported data breach involving credit cards used at Sonic restaurants could have affected millions of customers.
According to independent journalist Brian Krebs, who specializes in reporting on data breaches, 5 million credit and debit card accounts went on sale on an illicit website last week.
The sale of the leaked financial information claimed it included cards from "almost all USA states."
Krebs wrote that multiple banks reported a pattern of fraudulent purchases on cards that had been used at Sonic. It's unclear if Sonic was the only company impacted by the breach.
Sonic, which operates thousands of locations across 45 states, confirmed the breach to Krebs, telling him an investigation is in its early stages.
On Wednesday morning, after the news broke, Bloomberg reported that shares of Sonic stock fell as much as 4.4 percent within the day.
Clint Davis is a reporter for the Scripps National Desk. Follow him on Twitter @MrClintDavis. Keep up to date with the latest news by following @ScrippsNational on Twitter.