DAO Hack: In 2016, a decentralized autonomous organization (DAO) built on the Eth blockchain suffered a security breach, resulting in the theft of approximately one-3rd of its funds. The incident led to a hard fork in the Ethereum blockchain, resulting in the creation of Ethereum (ETH) and Ethereum Classic (ETC).

Bitfinex Hack: In 2016, Bitfinex, a prominent crypto exchange, was hacked, resulting in the loss of approximately 120,000 Btc. To compensate affected users, Bitfinex issued BFX tokens, which were later redeemed or converted into equity in the exchange.

Parity Wallet Bug: In 2017, a bug in the Parity multi-signature wallet smart contract led to freezing of approximately $160mil worth of ETH. The bug was accidentally triggered by a user, it highlighted the importance of thorough auditing and testing in smart contract.