SEAToken exploit analysis

SEAToken's transferWithFee debited the sender and credited the receiver, but reserved a fee amount that was later returned from the same balance. The fee was returned from the receiver's debited amount rather than from the contract's fee pool, so an attacker could call transferWithFee against the receiver with a small input and get a fee return against a larger recorded transfer.

DeFiHackLabs reconstructs the sequence against the live Arbitrum state; the drain is in 0x001cb16e17c4c5a5c4d02423c9e9b2f2b11ab6b2a1baf2ba53b8fcaf06167716 on Arbiscan for a total loss of about $110K.

What would have prevented it: a transferWithFee whose fee return reads the same fee pool that the contract holds, not the receiver's debited amount.