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Front-Running

Definition

Front-running is a deceptive practice in decentralized exchanges and other blockchain applications where a transaction is submitted and executed ahead of another known pending transaction. This is typically achieved by observing pending transactions in the mempool and then submitting a similar transaction with a higher gas fee to ensure it is processed first. The front-runner profits by exploiting the price impact of the original transaction, often leading to unfavorable outcomes for the victimized user. This practice undermines market fairness and can result in financial losses.