MasterCard warns of possible security breach, Visa also reportedly affected

MasterCard is investigating a possible breach of cardholder account data involving a U.S.-based payment processor, the company said Friday.

"As a result, we have alerted payment card issuers regarding certain MasterCard accounts that are potentially at risk," the Purchase, N.Y., credit-card company said in a statement.

Law enforcement officials have been notified of the matter and an "independent data security organization" is conducting an ongoing forensic review. The U.S. Secret Service is investigating the breach, a spokesman said Friday.

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