Tegro

The transaction executor can be anyone who can enter the matchedAmount. The matchedAmount can be entered in the way where the calculated baseFeeAmount would be rounded down to 0.E.g While calculating fee on L207 if the feeAmount is 20 and matchedAmount is 499 then the calculation would be: 499 * 20 / 10000 = 0 (In solidity). The same can happen while calculating quoteFeeAmount using totalPrice. The above example shows that if the numerator is less than the denominator then the answer can be rounded down to 0 which will allow an executor to bypass the fees on a small portion of the amount. The successful attack depends on the amount of tokens that are getting sold/bought, but to perform this attack recursively to bypass the fee, it might not be feasible as every transaction would cost the gas (also depends on who pays the fee or who is executing the signed orders). But it would be good practice to add a lower limit for the amount so that if the matchedAmount is less than that specified limit then the transaction will revert.

While using fee-on-transfer tokens (as baseToken or quoteToken), the amount that will get actually transferred would be less than what is getting transferred because of fee deductions.This doesn’t create any security issues but can create confusion on the receiver side.