It is open to developers as well as a door left ajar for bad actors.
Written by: 0x
Compilation: Chopper, Foresight News
It’s time to face the real problems that exist with the Uniswap v4 Hook mechanism.
This year, the 0x protocol has completed 81.92 million transactions, with total transaction volume reaching $42.67 billion; about 70% of transactions use Uniswap’s liquidity pools.
Every month, we receive dozens of requests to review and integrate v4 Hooks—good and bad cases alike. But recently, a large number of malicious cases have begun to emerge.
Hook can indeed enable a number of practical functions, including custom trading rules and liquidity management. This article is not saying that these application scenarios should not exist, nor is it opposing developers building based on Hook; an unlicensed Hook mechanism introduces brand-new trade-off risks to trade execution and aggregation. A typical problem is that some malicious pools return quotes to the outside that do not match the assets users actually receive.
In the past few weeks, 0x has observed a sharp increase in the number of malicious Uniswap v4 Hooks. These malicious Hooks return one price when a quote request is made, but use a different set of prices when the settlement executed trade occurs. Malicious Hooks can be implemented in many ways, but the final outcome is the same: by deceiving aggregators, wallets, and trading applications, they steal users’ assets.
Below are the phenomena we observed on-chain, along with the mitigations that 0x has already taken.
The problem with the Hook mechanism: it is open to developers, but it also swings wide the door for bad actors
First, the pros: v4 Hooks bring a layer of innovation to automated market makers (AMMs). Developers can build AMMs with custom logic that runs at key lifecycle nodes of a pool—such as before and after the swap happens, or when liquidity providers’ positions change. Hooks can implement arbitrary logic and anyone can deploy them; once deployed, they can directly reuse the traffic from the DeFi ecosystem’s most widely integrated liquidity networks.
This is the core contradiction. While this mechanism provides legitimate developers with stronger liquidity and transaction-execution customization capabilities, it also makes it difficult for aggregators to identify which pools are trustworthy.
Besides lowering the development threshold for developers, Hooks also provide ample room for malicious actors. Malicious Hook projects don’t need to build a well-known brand, don’t need to guide users to visit a standalone frontend, and don’t need to obtain traffic from zero cold-start. They only need to return extremely enticing quotes to various liquidity aggregators.
When an aggregator sees the best quote, it routes the transaction to that pool. But wallets and trading apps rely on the results output by the aggregator—so a malicious pool can use the infrastructure the user already trusted to carry out the attack.
Current state of malicious Hooks
In the past 18 months, the number of Uniswap v4 Hooks has grown explosively. We conducted static and dynamic analysis on a total of 84,163 Hooks across 6 chains, and combined them with real deal/settlement data to review outcomes: only 19.4% are safe Hooks, 54.2% are malicious Hooks, and 26.4% are suspected malicious Hooks.
Data statistics as of 2026-09-11
Malicious modes vary: some are like rolling dice to randomly deduct fees, while others detect whether the EVM runtime environment is from a quote query. But the underlying behavior is highly consistent—the quoted prices returned by the route are not reliable prices the user can actually obtain. We observed that after transactions involving a malicious v4 Hook, the user’s actual received assets can shrink by up to 50% compared to the highest quote originally shown to the user.
Case 1
Hook address: 0x800cef53c3fd41109dffec62e5251bdd7acba5c7
Chain: Base
Trading pair: ETH/NVDAc
Total number of executed trades: 6,516
Number of fee-charged executed trades: 3,946 (60.6%)
Fee range: 0–18%
Median fee deducted across all executed trades: 17.96%
Median fee deducted for executed trades where a fee was charged: 18%
Total fees collected (USD): $143,037
Data as of September 11, 2026
Case 2
Hook address: 0x141984423d1a28242b3dd8888c5b0daa7b13c880
Chain: BNB Chain
Trading pair: USDT/WBNB
Total number of executed trades: 4,879
Number of fee-charged executed trades: 1,619 (33.2%)
Fee range: 0–12.8%
Median fee deducted across all executed trades: 0%
Median fee deducted for executed trades where a fee was charged: 12.8%
Total fees collected (USD): $18,592
Data as of September 11, 2026
Conclusion
The original intention of designing Hooks is to improve Uniswap’s extensibility, but it has also spawned a large amount of abuse risk. Permissionless extensibility brings an unavoidable trade-off in terms of transaction execution and trust. No one—route contracts, applications, or ordinary users—can ignore this risk.
This summer’s market reality proves that permissionless liquidity is not the same as trusted liquidity. Just like the earlier Prop AMM fiascos, this flexibility for developers to customize swap logic also provides a new way for malicious actors to manipulate trades.
Based on the observations above, we propose the following insights:
A route contract must verify that the quote returned by the pool matches the actual execution result;
All kinds of applications need the ability to quickly filter out suspicious transaction routes.
Users need to understand that a displayed best quote is meaningful only when the route behind it is safe.