A sandwich attack is a type of exploit used in decentralized finance (DeFi) trading. It occurs when an attacker places two orders around a target transaction that is about to be executed.First, the attacker identifies a pending transaction that will affect the price of an asset, usually a large buy order. The attacker then quickly places a buy order with a higher gas fee to ensure it gets processed first. This order pushes the asset’s price up due to increased demand. Once the attacker’s buy order is completed and the price has risen, they immediately place a sell order at the new, higher price. The original victim’s transaction is then executed at this inflated price, causing them to pay more than they would have without the sandwich attack.This technique exploits the transparency of blockchain transactions, where pending orders can be observed. It highlights vulnerabilities in automated trading and the potential for malicious actors to profit at the expense of others.