0x Calls Uniswap v4 Hooks a Mistake, and Uniswap's Founder Replies "Skill Issue"
0x says most Uniswap v4 hooks are malicious
On Sept. 14, 0x, a service that searches decentralized exchanges for the best prices, published research titled "Uniswap v4 hooks were a mistake." Hooks are custom add-on programs that anyone can attach to a Uniswap v4 trading pool to change how it works.
0x said most of the hooks it studied quote one price and then settle the trade at a worse one. Uniswap founder Hayden Adams replied early on Sept. 15 with two words: "skill issue." He did not dispute 0x's figures and argued the problem is how 0x routes trades, not the hooks themselves.
The numbers behind the claim
- 0x analyzed 84,163 hooks across six chains using static analysis, dynamic analysis and observation of settled trades.
- As of Sept. 11, it classified 19.4% as safe, 54.2% as malicious and 26.4% as likely malicious.
- Trades routed through malicious v4 pools delivered "as much as 50% less at execution than the amount quoted to the user," 0x said.
- 0x said it has routed 81.92 million trades and $42.67 billion in volume this year, with about 70% of its transactions touching Uniswap liquidity.
Two live hooks that charged hidden fees
0x named two hooks now running. One, on the Base network, pairs ETH against NVDAc. It took fees on 3,946 of 6,516 fills, a rate of 60.6%, with a median fee of 18% when charged and $143,037 collected in total.
A second, on BNB Chain, pairs USDT against WBNB. It charged fees on 1,619 of 4,879 fills at rates up to 12.8%, collecting $18,592.
0x said the tricks vary. "Some operate like a dice roll, some inspect the EVM environment to detect quoting," the post said, with the same result: the hook only has to look like the best quote to the systems that search for liquidity.
Duncan Townsend, a smart contract engineer at 0x, said the company "put in a phenomenal amount of work to get hooks to work correctly in 0x API, but fundamentally they set bad expectations between hook authors and aggregators." He said simulating a trade before quoting does not help, because "hooks often detect simulation and conceal their behavior."
Uniswap's founder calls it a skill issue
Adams said routers should not send orders to bad hooks and pointed developers to Uniswap's own API, which he said avoids malicious hooks, reaches all Uniswap liquidity without added fees, and now also aggregates outside liquidity.
"v4 hooks have unlocked huge amounts of innovation," he wrote, calling the 0x post a waste of time. In another reply he compared it to saying "ethereum is bad because you can make malicious smart contracts."
Adams also said the StablePair hook Uniswap Labs released on Sept. 10 is now the highest-volume pool on Ethereum and is earning higher returns for liquidity providers. Only Uniswap Labs can create pools against that hook on Ethereum.
Hours later he broadened the argument: "Any sufficiently useful new technology deals with scams. Phone calls, text messages, email, websites, social media etc - all rife with scam content, no filtering system is perfect." Uniswap's Niko Kampouris called the 0x headline clickbait and said traders should "just use the uniswap api, where all hooks are vetted."
The argument over Uniswap's allowlist
Dan Robinson, general partner and head of research at Paradigm, a Uniswap investor, said the post "should be titled '0x routing made a mistake'" and linked to Uniswap's hook allowlist. "If you're an aggregator, you can't just route to arbitrary hooks," he wrote. He later noted there is no approval process for creating a hook, and that every aggregator chooses which hooks to route to. He compared 0x's complaint to "someone saying 'ERC-20 was a mistake because I bought an ERC-20 token and it turned out to be worthless.'"
Uniswap's allowlist documentation says submission is required only if a hook uses a delta flag, has a deployment address starting with 0x91, or targets major token pairs. Everything else is approved automatically. The docs say upgradable hooks and hooks that require custom data inputs are not approved.
Townsend said 0x already uses that list, and that it is not enough. "There's at least one malicious hook on that list and many good hooks that need to be routed faster than they can get added to the list," he wrote. He posted a link to what he described as an upgradeable hook whitelisted by the Uniswap interface, plus a transaction he said the Uniswap interface itself routed through a malicious hook. These claims are reported by 0x and have not been independently confirmed.
Another view: the fix is onchain routing
Keone Hon, co-founder of Monad, said the behavior 0x documented first appeared in proprietary market makers and later moved to v4 hooks. Malicious makers alternate between very tight and very wide quotes, he wrote: the tight quote wins the route, the wide one executes.
Slippage limits, which cap how far the executed price can move from the quote, stop some of those trades, Hon said, but "many users set their slippage settings far too permissively. Those users get taxed brutally." He said the real fix is fully onchain order routing, which needs a virtual machine fast enough to run routing logic at execution time. He added that the spoofing window exists "because the aggregator chooses the route before the tx is signed."
What is confirmed
- 0x published the research on Sept. 14; Adams replied early on Sept. 15.
- 0x's stated analysis covered 84,163 hooks across six chains and classified 54.2% as malicious and 26.4% as likely malicious as of Sept. 11.
- Uniskwap v4 launched its hook architecture in February 2025.
- Uniswap v4 holds $1.06 billion in total value locked, up 39.9% over 30 days, according to DefiLlama. The protocol processed $38.12 billion in exchange volume over that period, led by Robinhood Chain at $15.94 billion and Ethereum at $12.56 billion.
- UNI traded at $6.35 on Sept. 15, up 1.5% on the day and down 9% over the week, according to CoinGecko.
What is still unclear
The two sides disagree on who is responsible when a permissionless pool advertises a price it does not honor. 0x says hook design pushes that cost onto routers and the wallets and apps built on them. Uniswap and Paradigm say aggregators should vet which hooks they route to, and that Uniswap's own router already does.
0x's claim that Uniswap's own interface routed a transaction through a malicious hook, and its claim that an upgradeable hook sits on the allowlist, are its own assertions and have not been independently confirmed.
Why it matters
The dispute matters because it determines who protects users when a quoted price is not the price they get. If 0x is right, the v4 hook design makes it easy for bad actors to reach users through the aggregators that search for prices. If Uniswap and Paradigm are right, the safety layer belongs to the routing services, and aggregators that fail to vet hooks are the ones at fault.
The stakes are visible in the numbers: 0x says about 70% of the trades it routes touch Uniswap liquidity, and Uniswap v4 alone holds $1.06 billion in locked value.