Robinhood Data Breach Nightmare Hinged on Customer Service Slip

Robinhood Markets Inc. caught criticism last year for its shortcomings in customer support. After racing to staff up, the company has a new problem: a customer service representative mishap allowed a hacker to steal the personal information of about 7 million users.

The Menlo Park, California-based brokerage app is reeling from the largest hack in its history, which compromised private details of about one-third of its users. A company statement said the Nov. 3 breach hinged on a phone call where the hacker duped a customer support staffer. It didn’t provide details on how exactly the culprit gained entry.

The ...