Submitted by cccz
When a user fulfills an order using SeaportProxy, fees are charged in the \_handleFees function based on orders.price.
According to the Seaport documentation, Seaport allows partial fulfillment of orders, which results in too much fee being charged when an order is partially filled
https://docs.opensea.io/v2.0/reference/seaport-overview#partial-fills
Consider feeBp == 2%
The order on Seaport has a fill status of 0/100 and each item is worth 1 eth.
User A fulfills the order using LooksRareAggregator.execute and sends 102 ETH, where order.price == 100 ETH.
Since the other user fulfilled the order before User A, when User A fulfills the order, the order status is 99/100.
Eventually User A buys an item for 1 ETH but pays a fee of 2 ETH.
https://github.com/code-423n4/2022-11-looksrare/blob/e3b2c053f722b0ca2dce3a3eb06f64859b8b7a6f/contracts/proxies/SeaportProxy.sol#L136-L147
Consider charging fees based on the users actual filled price.
0xhiroshi (LooksRare) confirmed and commented:
