Poly Network Hack: The $610M Exploit and DeFi Lessons

On August 10, 2021, an attacker drained approximately $612 million from Poly Network, a cross-chain interoperability protocol, in what was at the time the largest decentralized finance exploit on record, exposing a systemic vulnerability in how assets move between blockchains and forcing every DeFi participant to confront a risk most had underweighted. The documented loss was approximately $612 million, not $6.4 billion, according to Chainalysis on-chain analysis of the August 2021 incident.