Yet another smart contract bug
Recently, a hidden DoS bug (called Gridlock) was revealed in Edgeware's Lockdrop smart contract that has locked hundreds of millions of dollars worth of Ether. Because of this bug, Edgeware had to newly deploy the fixed version of the contract, and as a result, two Lockdrop contracts (old version and new version) currently live in parallel on mainnet. (This means that you can send a transaction to either of these contracts to lock your Ether, until the old one is attacked and becomes incapable.)
In this article, we will review the Gridlock bug and discuss how formal verification can help to prevent this type of bugs.