Attackers used the data to contact victims and trick them into sending money.

Coinbase Global Inc.’s stock fell Thursday after it said it’s working with law enforcement to track down an unknown “threat actor” that paid its contractors working in support roles for the company outside the U.

Coinbase Global said Thursday that it has refused to pay a $20 million ransom demand from cybercriminals who bribed the company’s overseas customer support agents to steal sensitive user data.The cryptocurrency exchange estimated that the incident could cost from $180 million to $400 million,