Though the team didn't disclose an exact amount, a wallet address circulated by NiceHash users suggest that as many as 4,736.42 BTC – an amount worth more than $62 million at current prices – has been stolen.
The NiceHash team urged users to change their non-NiceHash online passwords as a result of the breach and subsequent theft.
"While the full scope of what happened is not yet known, we recommend, as a precaution, that you change your online passwords," they wrote in the statement.