The decentralized finance (DeFi) ecosystem is facing a major stress test following the discovery of a critical vulnerability in versions 0.2.15, 0.2.16, and 0.3.0 of the Vyper programming language. The vulnerability allowed malicious actors to exploit a malfunctioning reentrancy lock, resulting in the theft of millions of dollars worth of cryptocurrencies on July 30. The attack specifically targeted four liquidity pools on the Curve Finance protocol, namely aETH/ETH, msETH/ETH, pETH/ETH, and CRV/ETH. According to Curve Finance, the impact was severe, with all the vulnerable pools being drained completely.