GMX Hacker Returns Funds After $42M Exploit

GMX, a decentralized exchange on Arbitrum, suffered a major exploit on July 9, 2025, when a hacker stole over $40 million in crypto assets by exploiting a re-entrancy vulnerability in its V1 contracts. In response, GMX halted trading and offered a 10% white-hat bounty and legal immunity for the return of funds. The attacker subsequently returned approximately $40.5 million, netting a profit of about $3 million after retaining the bounty and benefiting from ETH price fluctuations, with the recovery verified by firms such as PeckShield. This led to a sharp rebound in GMX's token price, rising as much as 16%. GMX pledged to compensate affected users and conduct further security reviews. The incident highlights ongoing DeFi vulnerabilities and the increasing use of negotiated recoveries to mitigate losses.