Hundred Finance, a multichain lending protocol, has suffered a security breach on the Ethereum layer-2 blockchain Optimism, resulting in losses of $7.4 million. The protocol has reported that it is working with various security teams and has contacted the attacker. The method of the attack has not been disclosed by Hundred Finance, but blockchain security firm Certik has identified it as a flash loan attack.
The attacker manipulated the exchange rate between ERC-20 tokens and hTOKENS, enabling them to withdraw more tokens than originally deposited. This comes a year after Hundred Finance was exposed to another attack on the Gnosis Chain, where over $6 million was lost. Flash loan attacks have been used to target DeFi protocols in recent times, including attacks against Euler Finance ($196 million) and Mango Markets ($46 million).