Uniswap v4 Pool's 0% Fee Quote Hides 12.8% LP Charge

A Uniswap v4 dynamic fee pool on BNB Chain was found to have a 'toxic' design, where users were quoted a 0% fee but actually paid a 12.8% LP fee on execution.

Between August 22 and 23, 2026, the pool processed 21,086 trades, accumulating $131,888 in fees before being deregistered.

The mechanism behind this 'poison pool' involved three layers of determination: distinguishing the caller, checking gas, and applying per-transaction pseudo-randomness to the fee rate.

Although the transaction could still succeed after the fee was taken, due to a large buffer in the output amount, this design allowed the deployer to benefit from the divergent fees.

The whitelist logic kept other LPs out, and the 0% tier was used for wash trading, further benefiting the deployer.