On July 30, Curve Finance suffered exploits on a number of its stable pools that were using Vyper, which is a smart contract programming language for the Ethereum Virtual Machine (EVM). Curve alerted its users that alETH, msETH, and pETH stable pools using Vyper 0.2.15 have been exploited “as a result of a malfunctioning reentrancy lock.” It added that crvUSD contracts and any pools with it were not affected. Curve operates 232 different pools, but only ones using these versions of Vyper were affected.