NiftyApes - Seller Financing

`_makePayment()` currently allows payments to a sanctioned seller. If a buyer refuses (or is under legal obligation not) to send funds to the sanctioned seller, once enough time has passed, the sanctioned seller can transfer the ticket to a non-sanctioned address and seize the NFT. If a sanctioned seller does this near the end of the payment plan, then they will have effectively stolen all the funds from the buyer.

Any offerings that are not WETH are locked forever after fulfilling a Seaport order. `_validateSaleOrder()` does not ensure that the length of `order.parameters.offer[]` is 1, meaning that there could be offers accepted that receive tokens outside of WETH. Since only WETH is transferred to the buyer, any additional funds would be locked in the contract without a method to withdraw them.

Sanctioned users are allowed to transfer their buyer and seller tickets, as there is no check in `_transfer` to ensure the sending party is not sanctioned. A sanctioned user can easily transfer their ticket to a secondary address.

`_createLoan()` incorrectly assigns the `nftId` of both the `buyerUnderlyingNFT` and `sellerUnderlyingNFT` when financing collection offers. Collection offers have the `offer.nftId` value assigned as `~uint256(0)`, which is used to denote that the offer exists for the entire collection instead of an individual NFT. When buying from a collection offer, the buyer specifies the individual NFT they are purchasing in `nftId` field in `buyWithFinancing()`. However, the individual `nftId` is not assigned to the buyer and seller's underlying NFT, rather the `offer.nftId` is, which would be the maximum value for a `uint256`. This incorrect assignment would break the delegate.cash functionality if a buyer transfers their ticket, as delegate.cash would be attempting to delegate an NFT that does not exist.

In `sellAsset()`, the total consideration is calculated as follows: ``` uint256 totalConsiderationAmount; for (uint256 i = 1; i < order.parameters.totalOriginalConsiderationItems; i++) { totalConsiderationAmount = order.parameters.consideration[i].endAmount; } ``` This is equivalent to setting the total consideration to the final element of `order.parameters.consideration[]` rather than the sum of the array. The contract will be unable to fulfill any Seaport orders that have multiple WETH considerations because it hasn't approved enough WETH to send to the Seaport contract.

`SellerFinancing` is intended to be the implementation contract for an upgradeable proxy, as it contains an `initialize()` function. Currently, anyone can call the `initialize()` method and write state variables to this contract. This could lead to an attacker taking control of the implementation contract.

The contracts currently use Solidity version 0.8.13. This version is not on the [list of recommended versions](https://github.com/crytic/slither/wiki/Detector-Documentation#incorrect-versions-of-solidity).

`__ERC721URIStorageUpgradeable_init()` is not called on construction. Although it does nothing in this version of the Open Zeppelin contracts, it is still a best practice to include this to support future upgradeability.

All privileged permissions should be clearly documented for users. The owner has the ability to arbitrarily set `royaltiesEngineContractAddress`. A custom version of this contract could redirect 100% of payments made to the owner. Additionally, these functions can all be invoked by the owner and modify core state addresses of `SellerFinancing`: - `updateRoyaltiesEngineContractAddress()` - `updateDelegateRegistryContractAddress()` - `updateSeaportContractAddress()` - `updateWethContractAddress()` - `pause()`, `unpause()` - `pauseSanctions()`, `unpauseSanctions()` As well as these functions in `MarketplaceIntegration`: - `updateSellerFinancingContractAddress()` - `updateMarketplaceFeeRecipient()` - `updateMarketplaceFeeBps()` - `pause()`, `unpause()` - `pauseSanctions()`, `unpauseSanctions()`

The `withdrawOfferSignature()` is restricted by the `whenNotPaused` modifier. Sellers should have the freedom to revoke their signatures at any time.