Summary

The zero address check for i_arbiter is in the initiateDispute function instead of constructor.

Vulnerability Details

The zero address check for i_arbiter is in the initiateDispute function. Therefore, if zero address is initialized for i_arbiter in the constructor then there is no way for the buyer or the seller to initiate a dispute using the initiateDispute function.

Instance:

https://github.com/Cyfrin/2023-07-escrow/blob/main/src/Escrow.sol#L103

function initiateDispute() external onlyBuyerOrSeller inState(State.Created) {
    if (i_arbiter == address(0)) revert Escrow__DisputeRequiresArbiter();
    s_state = State.Disputed;
    emit Disputed(msg.sender);
}

Impact

There is no way for the buyer or the seller to initiate a dispute resulting in the price getting locked if the buyer does not call the confirmReceipt function.

Tools Used

Manual review and VS Code

Recommendations

Zero address check should be present in the constructor instead of the initiateDispute function.
Add the below check in the constructor:

    if (i_arbiter == address(0)) revert Escrow__DisputeRequiresArbiter();