Poly Network's $611 Million Theft

In August 2021, Poly Network experienced a hack that resulted in the theft of over $611 million in various cryptocurrencies by exploiting a smart-contract vulnerability, though most of the funds were eventually returned.

The top 3

  1. Largest DeFi Hack (Then): The Poly Network exploit of August 2021, at $611 million, was the biggest decentralized finance (DeFi) theft at the time, though later surpassed by other major crypto breaches like Ronin Network's $624 million in March 2022.
  2. The White Hat Hacker's Full Return: In an unprecedented move, the anonymous hacker, who called themselves 'Mr. White Hat,' returned all $611 million in stolen assets over a period of 15 days, claiming their motivation was to expose vulnerabilities and secure the network.
  3. Cross-Chain Smart Contract Exploit: The Poly Network hack exploited a cryptographic flaw in its smart contracts, allowing the attacker to create a malicious parameter and bypass the bridge's validation process to withdraw tokens across Ethereum, Binance Smart Chain, and Polygon.

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