0x just dropped a long post ranting about hooks' side effects, and it also indirectly solved the mystery of those 0% fee pools I encountered a few days ago. In short, these malicious hooks disguise themselves with attractive prices during the quoting phase but switch to a different price or add extra fees during the actual settlement. This tricks aggregators, wallets, and trading apps, ultimately skimming profits off users. For example, those 0% fee pools—these hooks have `beforeSwap` and `afterSwap` permissions, allowing them to check conditions or reject transactions before execution. They can also alter the final settlement amount. So even if the PoolManager itself processes swaps at a 0% core fee, the hook can still apply custom charges before or after the swap. If it fools the aggregator, the end user ends up taking the hit. 0x shared some data after analyzing 84,163 hooks across six chains: - 19.4% are safe - 54.2% are clearly malicious - 26.4% are likely malicious Honestly, I think this is something aggregators need to work harder on. The original intent of hooks was to make Uniswap more extensible, but it also opened the door for abuse. It’s similar to smart contracts—they’re permissionless, so malicious behavior is inevitable. The contracts themselves can’t distinguish between good and bad actors, so it’s up to app developers to fight against this stuff.