Incorrect calculated fee reward for ERC20Quest

[code423n4]

Lines of code

https://github.com/rabbitholegg/quest-protocol/blob/8c4c1f71221570b14a0479c216583342bd652d8d/contracts/Erc20Quest.sol#L96-L98
https://github.com/rabbitholegg/quest-protocol/blob/8c4c1f71221570b14a0479c216583342bd652d8d/contracts/Erc20Quest.sol#L89-L93
https://github.com/rabbitholegg/quest-protocol/blob/8c4c1f71221570b14a0479c216583342bd652d8d/contracts/Erc20Quest.sol#L100-L104

Vulnerability details

Impact

More than enough funds might be redeemed from ERC20Quest.

Proof of Concept

1. Quest finished.
2. Only one user withdrawn their funds.
3. Function withdrawFee has been executed.
4. Another one user withdrawn their funds.
5. Function withdrawFee has been executed. -- But here protocolFeeRecipient will receive fees for TWO users, Although it should has received only for one.

Tools Used

Manual audit

Recommended Mitigation Steps

As I mentioned early add possibility to call withdrawFee() only once.

And in protocolFee() instead of calculating fees only for redeemed users calculates fee over all users.

    function protocolFee() public view returns (uint256) {
        return (maxTotalRewards() * rewardAmountInWeiOrTokenId * questFee) / 10_000;
    }

---

But your idea may be to send commissions only for those users who participated.
In this case, you need to allow withdrawFee() to be called as many times as you want, but at the same time maintain the number of commissions already withdrawn and the number of participants who have collected their awards.
Like this:

uint256 receivedFeesFoUsers;


function withdrawFee() public onlyAdminWithdrawAfterEnd { // TODO DON'T FORGET ADD REENTRANCY GUARD
    uint256 newUsers = receiptRedeemers() - receivedFeesFoUsers;
    receivedFeesFoUsers = receiptRedeemers(); 
    uint256 fee = (newUsers * rewardAmountInWeiOrTokenId * questFee) / 10_000;
    IERC20(rewardToken).safeTransfer(protocolFeeRecipient, fee);
}

[c4-judge]

kirk-baird marked the issue as duplicate of #23

[c4-judge]

kirk-baird marked the issue as satisfactory