What Is a ‘Maximum Extractable Value’ (MEV) Attack and How Is It Related to Transaction Privacy?

MEV is the profit a validator or miner can extract by arbitrarily including, excluding, or reordering transactions within a block beyond the standard block reward and gas fees. Front-running is a form of MEV, where a party observes a large pending transaction in the public memory pool (mempool) and uses that non-private information to profit.

The lack of transaction privacy in the mempool is what enables many MEV attacks.