On July 13, a whale attempted to swap 50 million USDT for AAVE tokens through Aave's frontend interface. Due to severe liquidity shortage, extreme slippage resulted in receiving just 324 AAVE—worth roughly $36,000—inflicting a nearly $50 million loss, the largest single-trade slippage disaster in DeFi history.
On-chain data shows the trade was routed via CoW Protocol, a decentralized aggregator. Before execution, Aave's interface displayed a clear warning about extreme price impact, requiring the user to check a confirmation box. The user nonetheless confirmed on a mobile device, accepting the doomed parameters. Slippage occurs when the expected price deviates from the actual fill price; when order size far exceeds market depth, slippage can explode—this case featured both factors at extreme levels.
CoW Protocol: Trade Executed as Signed, System Warned Clearly
CoW Protocol later stated: "Earlier today, a trader attempted to swap 50 million aEthUSDT for aEthAAVE via Aave's swap interface (powered by CoW Protocol). Despite explicit warnings that the trade would lose almost all value, and the user having to actively opt-in after seeing the warning, the user still proceeded." From the protocol perspective, this was neither a technical glitch nor a hack; it was a case where the user saw the warning yet confirmed. The team acknowledged: "Such trades show DeFi UX still needs to protect all users. We're working on balancing strong safeguards with user autonomy."
Aave: Willing to Refund ~$600K in Fees
Aave's team, though not at fault, expressed sympathy. They are actively reaching out to the whale and are willing to refund roughly $600,000 in fees collected from the trade. But against a $50M loss, $600K is a drop in the bucket. The incident once again underscores the core risk in DeFi: even with thorough warnings, a single moment of carelessness or misjudgment can lead to irreversible catastrophic losses. For large traders, slippage settings and batch execution remain critical—never dump full capital into one swap.