Attackers conducted a 51% attack on Ethereum Classic to execute a double-spend against OKEx. They deposited ETC, withdrew it, then reorganized the blockchain to erase the deposit transaction while keeping their funds, resulting in a net $5.6M theft via unconfirmed transaction reversal.

OKEx has confirmed that the latest 51% attack caused ETC losses of approximately $5.6 million. Out of concerns about the security of the ETC mainnet, it is considering removing ETC from the exchange. According to a report released by OKEx on Saturday, OKEx will repay all the ETC lost by users.