The decentralized lending platform Euler Finance suffered a flash loan attack in which an exploiter stole $197 million from the project. The attacker stole $8.7 million in the Dai stablecoin, $18.5 million in wrapped Bitcoin, $135.8 million in Lido staked Ethereum (stETH), and $33.8 million in the USDC stablecoin. Although Euler was well known for its many code audits, the project had later added a vulnerable function that had not been as heavily audited.
Euler announced that they were aware of the exploit, and were "working with security professionals and law enforcement".
On April 3, Euler Finance announced that they had completed successful negotiations, and that "all of the recoverable funds taken from the Euler protocol on March 13th have now been successfully returned by the exploiter". Unfortunately, based on on-chain transfers, this appeared to only be around $31 million.