BOSTON—Kroger says personal data, including Social Security numbers of some of its pharmacy and clinic customers, may have been stolen in the hack of a third-party vendor’s file-transfer service. The Cincinnati-based grocery and pharmacy chain said in a statement Friday that it believes less than 1 percent of its customers were affected—specifically some using its Health and Money Services—as well as some current and former employees because a number of personnel records were apparently viewed. It says it is notifying those potentially impacted, offering free credit-monitoring. Kroger said the breach did not affect Kroger stores’ IT systems or grocery store systems or data and there has so far been no indication of fraud involving accessed personal data. The company, which has 2,750 grocery retail stores and 2,200 pharmacies nationwide, said Sunday in response to questions from The Associated Press that an investigation into the scope of the hack was ongoing. …