A user attempting to swap $50 million worth of USDT for AAVE through the Aave interface ended up receiving only 324 AAVE, after confirming a transaction that had already triggered severe execution warnings. The trade has drawn attention to the limits of front-end safeguards in DeFi, especially when very large orders meet thin liquidity.
According to Aave founder and CEO Stani Kulechov, the interface flagged the transaction because of extraordinary slippage, but the user approved the warning on a mobile device and proceeded anyway. The result was far worse than a normal market order outcome. The main issue was not simply slippage at execution, but the fact that the quoted trade already carried an extremely bad rate before fees and final settlement.
The core problem was a 99% price impact quote
Aave developer Martin Grabina broke down the mechanics behind the trade. He said slippage is the tolerance buffer on a market order, covering the difference between the quoted price and the final fill caused by market movement between signing and execution. In this case, though, the central problem was a quote showing a 99% price impact.
Grabina said Aave’s interface calculates slippage suggestions algorithmically based on asset volatility and order size, while users can also change the slippage setting or use limit orders to reduce execution risk. Here, the user accepted an extremely poor rate before fees and slippage were even applied. The quote field on the order showed an original rate of $50 million USDT for fewer than 140 AAVE.
Aave to return fees as CoW Swap routing operated as designed
Stani.eth said DeFi should remain open and permissionless, but added that the industry can still build extra guardrails to better protect users. Aave said it plans to contact the user and return about $600,000 in fees collected from the transaction.
He also said the CoW Swap routers functioned as intended and that the integration followed standard industry practice. Grabina added that, despite the disastrous outcome, the user still received a 0.7% surplus through CoW Swap’s auction mechanism. That detail suggests the execution path worked as designed, while the incident exposed how little protection users may face when approving extreme-size DeFi trades at highly unfavorable quoted prices.