Submitted by WatchPug, also found by 0xsanson, and shenwilly
In the current design/implementation, while the order is executed by the MATCH_EXECUTOR, the gas cost will always be paid by the maker orders buyer.
While the buyer did agreed to pay a certain price for certain NFTs, the actual cost for that maker buy order is unpredictable: because the MATCH_EXECUTOR can choose to execute the order while the network is extremly busy and the gas price is skyhigh.
As the gas cost at whatever gas price will be reimbursed by the buyer, the executor has no incentive to optimize and choose to execute the order at a lower gas cost.
The result is the buyer can sometimes end up paying much higher total price (incl. gas cost) for the items they bought.
While this is more of a design issue than a wrong implementation, the impact can be very severe for some users, and can cause defacto fund loss to the users who have they maker buy orders matched at a high gas price transactions.
Consider adding a new paramer to maker buy orders, maxGasCost to allow the buyer to limit the max gas they agreed to pay.
nneverlander (Infinity) acknowledged, but disagreed with severity and commented:
HardlyDifficult (judge) decreased severity to Medium and commented:
