What Are “Sandwich Attacks” in the Context of MEV?

A sandwich attack is a type of Miner Extractable Value (MEV) exploitation where a malicious actor places two transactions around a victim's pending transaction in the same block. The attacker first places a buy order just before the victim's trade, driving the price up.

The victim's trade executes at the worse, higher price. Immediately after, the attacker places a sell order to profit from the price increase, effectively "sandwiching" the victim's trade and extracting value.