A crypto user has lost millions of dollars to slippage and Maximal Extractable Value (MEV) bots while performing a swap involving the decentralized finance protocol Aave.

 

The user whose Binance wallet was funded attempted to swap $50.4 million in USDT for the AAVE token using the decentralized exchange aggregator CoW Protocol and the decentralized exchange SushiSwap.

 

Since DEXs like SushiSwap use automated market makers (AMMs) that set token prices based on trading activity, the user was warned about the potential for high slippage.

 

“Given the unusually large size of the single order, the Aave interface, like most trading interfaces, warned the user about extraordinary slippage and required confirmation via a checkbox,” Stani Kulechov, Aave’s founder, said.

 

The user ignored the warning and proceeded with the swap, receiving only 327 AAVE tokens from the $50.4 million transaction. Due to extreme slippage, the user effectively paid about $154,000 per AAVE, far above the market price of $114.

 

“The user confirmed the warning on their mobile device and proceeded with the swap, accepting the high slippage, which ultimately resulted in receiving only 324 AAVE in return,” Stani added. 

 

Reacting to the incident, CoW Protocol, the DEX aggregator used for the swap, said on its X account, “Despite clear warnings that showed the user they would lose nearly all of the value of their transaction, and despite needing to explicitly opt into the trade after seeing the warning, the user chose to proceed with their swap.”

 

 

The MEV Bot Sandwich Attack

In addition to the massive slippage loss, the user also lost nearly $10 million to MEV bots. Maximal Extractable Value (MEV) bots monitor pending blockchain transactions and exploit them for profit. 

 

These bots typically execute a sandwich attack: they buy a token before a user places a large order, driving up the token’s price. Once the user buys at this inflated price, the bots immediately sell, profiting from the transaction.

 

MEV bots, spotting the pending USDt-to-AAVE swap, borrowed $29 million in wrapped ether (WETH) from Morph, used the funds to buy AAVE on Bancor, and then sold the AAVE tokens at an inflated price on Sushiswap before the swap was executed, netting $9.9 million in profit.

 

 

Compensation Plans

To compensate the user for the huge loss, Stani Kulechov, Aave’s founder, said Aave would return $600,000 in transaction fees collected from the transaction. CoW Protocol also said it would refund any fees collected from the transaction back to the user.