Discover Financial Services has alerted cardholders to a data breach but has not disclosed the extent of personal information compromised or the number of individuals affected.

The incident was detected by Discover on August 13, 2018, when the company learned user accounts may have been affected in a data breach. It reports the breach did not involve any Discover systems but the company is aware of a possible merchant data breach.

Financial firms are common targets for cybercrime, but this marks the second time in 2018 that Discover reported a security incident affecting users' credit cards to the California Attorney General, BleepingComputer points out. State law mandates that businesses working with residents must inform the attorney general if a data breach affects users' information.

In this case, the report states, there were two separate sample breach notifications filed with the attorney general's office, indicating there could be two collections of credit card data discovered, or two types of cards affected in the attack. Not all affected cardholders were issued a new card and account number.

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