MetaMask Mistake Leads to $9,500 Uniswap Transaction

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  • A MetaMask user has mistakenly paid $9,500 on a Uniswap transaction
  • The user set his transaction fees manually and mixed up ‘gas price’ and ‘gas limit’
  • The mistake is an expensive reminder than being your own bank has its drawbacks

A trader has asked for help after he accidentally paid $9,500 in ETH for a Uniswap transaction. The trader asked for assistance on Reddit through his username ProudBitcoiner, saying that he mixed up the gas limit and gas price fields, leading to the mammoth transaction fee of 23.5 ETH for a $120 trade.

Help needed! I payed 23.5172 ETH ($9500) for $120 Uniswap transaction by mistake from r/ethtrader

MetaMask Manual Gas Entry Leads to Overfilling

ProudBitcoiner was using the popular MetaMask wallet to make the transaction, which allows manual editing of the gas price and gas limit amounts. MetaMask typically autofills these amounts based on the average gas price at the time, but users have the ability to change the levels to whatever they want.

This ability to manually change the transaction on MetaMask is a double edged sword – it can mean that you can execute a Uniswap trade quickly and beat the rabble, but it also means that you can make very, very expensive errors:

Metamask didn’t populate the “Gas Limit” field with the correct amount in my previous transaction and that transaction failed, so I decided to change it manually in the next transaction (this one), but instead of typing 200000 in “Gas Limit” input field, I wrote it on the “Gas Price” input field, so I payed [sic] 200000 GWEI for this transaction and destroyed my life :/

Aaaaaand It’s Gone

ProudBitcoiner says that he contacted Ethermine, the miner who processed the block, but the chances of being able to get anything back are almost zero unless Ethermine are feeling in benevolent mood – once a blockchain transaction has been processed it is impossible to stop or revert them.

ProudBitcoineer’s MetaMask mistake is an expensive reminder that for all the benefits of being your own bank, having responsibility for your own money comes with the relevant levels of responsibility.