Sonic Drive-In, a fast-food chain with nearly 3,600 locations across 45 U.S. states, has acknowledged a plug affecting an unknown number of store defrayal systems. The ongoing hack may hold led to a fire sale on millions of stolen credit and debit card accounts that are now being peddled in shadowy underground cybercrime stores, KrebsOnSecurity has learned.The first hints of a cut at ok City-based Sonic came last week when I began audience from sources at multiple financial institutions who noticed a recent pattern of fraudulent transactions on cards that had all previously been used at Sonic.