What Is “Fee Sniping” and How Does It Relate to Transaction Prioritization?

Fee sniping is a malicious or opportunistic mining practice where a miner attempts to steal the transaction fees of a block that has already been found by another miner but not yet fully propagated and confirmed. It involves the second miner quickly building a new block on top of the first one, but replacing the first block's transactions with a higher-fee set from the mempool.

This practice is largely mitigated by modern consensus protocols and orphan block mechanisms.