An order can contain large number of addresses within the whitelist array of an order.
https://github.com/code-423n4/2022-06-putty/blob/3b6b844bc39e897bd0bbb69897f2deff12dc3893/contracts/src/PuttyV2.sol#L78
When the PuttyV2.fillOrder function is called, it will attempt to check if the caller is whitelisted by looping through the order.whitelist array. However, if order.whitelist array contains large number of addresses, it will result in out-of-gas error and cause a revert. Thus, this order can never be filled.
https://github.com/code-423n4/2022-06-putty/blob/3b6b844bc39e897bd0bbb69897f2deff12dc3893/contracts/src/PuttyV2.sol#L284
https://github.com/code-423n4/2022-06-putty/blob/3b6b844bc39e897bd0bbb69897f2deff12dc3893/contracts/src/PuttyV2.sol#L669
It is recommended to restrict the number of whitelisted addresses within an order to a upper limit (e.g. 30).
Although client-side or off-chain might have already verified that the number of whitelisted addresses do not exceed a certain limit within an order, simply relying on client-side and off-chain validations are not sufficient. It is possible for an attacker to bypass the client-side and off-chain validations and interact directly with the contract. Thus, such validation must also be implemented on the on-chain contracts.
