BaseFee will underflow if amountIn is lesser than it
Summary
During the StabilityBranch::initiateSwap if the amountIn is lesser than the baseFee user wont be able to get a refund in the refunSwap function because the transaction will revert when calculating the refundAmountUsd
Thou, the baseFeeUsd is a uint256 and the amountIn is a uint128, so the baseFeeUsd will underflow if the amountIn is lesser than it.
https://github.com/Cyfrin/2025-01-zaros-part-2/blob/35deb3e92b2a32cd304bf61d27e6071ef36e446d/src/market-making/branches/StabilityBranch.sol#L474
Recommendations
Inside the initiateSwap function there should be a check that the amountIn is greater than the baseFee and if it is not should revert the transaction.
Lead Judging Commences
initiateSwap can be called with amount < than base fee, making the refund function revert due to underflow - funds stuck
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