A crypto trader lost more than $215,000 on March 12 in a sandwich attack while swapping stablecoins. The incident happened on Uniswap v3’s USDC-USDT liquidity pool, once again exposing how Maximum Extractable Value (MEV) bots take advantage of traders in decentralized finance (DeFi).
The trader wanted to exchange $220,764 in USD Coin (USDC) for Tether (USDT), but within just eight seconds, a bot interfered and messed up the trade. As a result, they ended up with only $5,271 in USDT—losing nearly 98% of their money.
Data from an Ethereum block explorer reveals that an MEV attack targeted Uniswap v3’s USDC-USDT liquidity pool, which holds $19.8 million in locked value.
MEV bots work like high-frequency traders, looking for ways to profit from blockchain transactions. In this case, the bot temporarily pulled all the USDC liquidity from Uniswap v3’s USDC-USDT pool, then put it back right after the trader’s swap went through. This trick led to a terrible exchange rate, causing the huge loss.
According to Michael Nadeau, founder of The DeFi Report, the attacker paid Ethereum block builder “bob-the-builder.eth” a $200,000 tip from the total amount while keeping $8,000 as profit.
DeFi researcher “DeFiac” believes the same trader, using different wallets, might have fallen victim to six similar sandwich attacks in a single day. Two wallets—“0xDDe…42a6D” and “0x999…1D215”—were also hit, losing $138,838 and $128,003, respectively.
Some speculate these strange swaps could be an attempt to launder money. DefiLlama developer 0xngmi suggested that bad trades like this might be intentional, used to clean illicit funds by sending transactions privately to an MEV bot.
Initially, some blamed Uniswap, but CEO Hayden Adams clarified that these transactions didn’t happen through Uniswap’s official interface, which has MEV protection and slippage settings to help prevent such attacks.
This isn’t the first time something like this has happened. A while back, a trader put in $732,000 for a swap and walked away with just $19,000 because of a similar trick.
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