Open to developers, but also to malicious actors.

Written by: 0x

Compiled by: Chopper, Foresight News

It is time to face the real issues with the Uniswap v4 Hook mechanism.

This year, the 0x protocol has completed 81.92 million transactions, with a total transaction volume of $42.67 billion, approximately 70% of transactions calling Uniswap's liquidity pools.

We receive dozens of audits and applications to integrate v4 Hook every month, and we have seen both good and bad cases. However, recently, a significant number of malicious cases have begun to emerge.

Hooks can indeed implement many practical features, including custom trading rules and liquidity management. This article does not argue that these application scenarios should not exist, nor does it oppose developers building on Hook; the permissionless Hook mechanism introduces new risks in trading execution and aggregation. A typical issue is that some malicious pools provide quotes that do not match the assets users ultimately receive.

In the past few weeks, 0x has observed a sharp increase in the number of malicious Uniswap v4 Hooks. These malicious Hooks return a price during the quote request but use a different price at the actual settlement. The implementation modes of malicious Hooks vary widely, but the end result is the same: they deceive aggregators, wallets, and trading applications to steal user assets.

Below are the phenomena we have observed on-chain and the measures 0x has already taken in response.

Issues with the Hook Mechanism: Open to Developers, but also to Malicious Actors

First, the benefits: v4 Hooks bring a layer of innovative capability to automated market makers (AMM). Developers can build AMMs with custom logic, executing logic at key points in the pool's lifecycle, such as before and after swaps, and when liquidity provider positions change. Hooks can implement arbitrary logic, and anyone can deploy them; once deployed, they can directly leverage the traffic of the liquidity network with the highest integration in the DeFi ecosystem.

This is the core contradiction; while this mechanism provides legitimate developers with stronger liquidity and trading execution customization capabilities, it also makes it difficult for aggregators to discern which pools are trustworthy.

In addition to lowering the development threshold for developers, Hooks also leave a substantial operational space for malicious behavior. Malicious Hook projects do not need to build a well-known brand, do not need to guide users to visit independent front-ends, and do not need to acquire traffic from a cold start. They only need to return enticing quotes to various liquidity aggregators.

When aggregators see the optimal quote, they will route the trade to that pool. Wallets and trading applications rely on the aggregators' output, allowing malicious pools to commit their misdeeds leveraging the foundational infrastructure that users inherently trust.

Status of Malicious Hooks

Over the past 18 months, the number of Uniswap v4 Hooks has exploded. We conducted static and dynamic analyses of a total of 84,163 Hooks across six chains and reviewed the actual transaction data: only 19.4% belong to safe Hooks, 54.2% are malicious Hooks, and 26.4% are suspected malicious Hooks.

Data statistics as of 2026‑09‑11

Malicious behavior models vary: some are like dice games with random fees, while others detect the EVM runtime environment to identify whether it comes from a quote inquiry. However, the underlying behaviors are highly consistent; the quotes returned by routing are not the reliable prices users can actually obtain. We have observed that for transactions involving malicious v4 Hooks, the actual assets users receive can shrink by as much as 50% compared to the quotes initially shown to them.

Case 1

Hook Address: 0x800cef53c3fd41109dffec62e5251bdd7acba5c7

Chain: Base

Trading Pair: ETH/NVDAc

Total Transactions: 6,516

Fee Transactions: 3,946 (60.6%)

Fee Range: 0‑18%

Median Fee of All Transactions: 17.96%

Median Fee of Transactions with Fee: 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 Transactions: 4,879

Fee Transactions: 1,619 (33.2%)

Fee Range: 0‑12.8%

Median Fee of All Transactions: 0%

Median Fee of Transactions with Fee: 12.8%

Total Fees Collected (USD): $18,592

Data as of September 11, 2026

Conclusion

The original intention of designing Hooks was to enhance Uniswap's scalability, but it has simultaneously given rise to a significant amount of abuse risks. Permissionless scalability brings transactional execution and trust-based trade-offs that cannot be overlooked by routing contracts, applications, or ordinary users.

The current market situation this summer proves that permissionless liquidity does not equate to trustworthy liquidity. Just like the previous chaos with Prop AMMs, this flexibility that allows developers to customize exchange logic similarly provides malicious actors with new means to manipulate trades.

Based on the aforementioned phenomena, we propose a few insights:

• Routing contracts must verify the quotes returned by pools to ensure they are consistent with the actual execution results;
• Various applications need to have the capability to quickly eliminate suspicious trading routes;
• Users need to understand that the displayed best quote is only meaningful when the route behind it is safe.