What Mechanism on a DEX Makes It Vulnerable to Price Manipulation via Sandwich Attacks?

The Automated Market Maker (AMM) model used by most DEXs is the primary vulnerability. AMMs rely on a mathematical formula (e.g. x y=k) to determine asset prices, which changes with every trade.

A large trade shifts the ratio significantly, creating predictable price movement. The sandwich attacker exploits this predictable price impact.