DAO ForkHappened on July 20th, 2016On June 17th, 2016, a vulnerability found inside the DAO contract had been exploited to drain approximately 3.6 million ETH from the fund. Due to the way this contract was designed, these funds would be frozen for 28 days before they could be transferred.
If no action would have been taken, the attacker would single-handedly have owned around 4.4% of the total supply of ETH. Because of this, a controversial proposal (EIP 779) was drawn up in order to change the code of the attacker’s lockup contract so everyone would be able to withdraw their ETH from the DAO contract.
On July 20th, a majority of mining power supported a fork which implemented this change, while a smaller community decided to split off and rename the old chain to Ethereum Classic.
