Incident reportSmart-contract exploitEthereum
The DAO −$50M
So bad Ethereum split in two to undo it.
What happened
An early investment fund on Ethereum was drained of 3.6 million ETH through a reentrancy bug: the contract sent money before updating its own books.
Timeline
Jun 17
Funds start draining through the reentrancy bug.
Jul 20
Ethereum hard-forks to return the ETH.
Jul 2016
The unforked chain carries on as Ethereum Classic.
Aftermath
The fork gave the ETH back and created a philosophical split the community still argues about.
Date2016-06-17
Lost$50M
WhoNever identified
Code is law. Until it isn't.
Lesson Update the balance before you send the money.