Front-Running

Front-running in blockchain and decentralized finance (DeFi) is a predatory practice where an actor, typically a bot or a miner/validator, observes a pending transaction in the public memory pool (mempool) and inserts their own transaction with a higher gas fee to execute it first, profiting from the resulting price movement or state change. This manipulation of transaction order, often resulting in a "sandwich attack," exploits the transparency of public blockchains to extract value from unsuspecting users.