[JURIST] CardSystems Solutions, Inc. [corporate website] said Friday that the FBI told them to refrain from releasing any informing regarding a security breach [JURIST report] which potentially exposed over 40 million cardholders to fraud. CardSystems said they first discovered the breach on May 22 [press release] and were surprised by MasterCard's decision to inform its customers in light of the FBI's recommendation. MasterCard [corporate website] released a statement Friday saying that approximately 13.9 million of the cards belonged to its customers and the rest were other brands. AP has more.