Read the findings of the 2022 Web3 Security Report

```solidity=139
    function upgradeStake(uint256 _stakeId, uint256 _amount) external {
        require(_amount > 0, "deposit cannot be zero");
        require(_stakeId < stakes[msg.sender].length, "no such stake id");
        StakeInfo memory stakeInfo = stakes[msg.sender][_stakeId];
        require(stakeInfo.startTs > 0, "stake was deleted");
        require(
            block.timestamp < stakeInfo.term + stakeInfo.lastUpdateTs,
            "stake matured"
        );
        uint256 extraShares = _buyShares(_amount);
        uint32 blockTimestamp = uint32(block.timestamp);

        uint256 lBonusShares = _getBonusL(
            extraShares,
            stakeInfo.lastUpdateTs + stakeInfo.term - blockTimestamp
        );
        uint256 bBonusShares = _getBonusB(
            stakeInfo.shares + extraShares,
            stakeInfo.amount + _amount
        );

        totalShares =
            totalShares +
            extraShares +
            bBonusShares +
            lBonusShares -
            stakeInfo.bBonusShares;
        // update stake info
        stakes[msg.sender][_stakeId] = StakeInfo(
            stakeInfo.amount + _amount,
            stakeInfo.startTs + stakeInfo.term - blockTimestamp,
            stakeInfo.startTs,
            blockTimestamp,
            stakeInfo.shares + extraShares,
            stakeInfo.lBonusShares + lBonusShares,
            bBonusShares,
            lambda,
            getReward(msg.sender, _stakeId)
        );

        emit UpgradedStake(
            msg.sender,
            _stakeId,
            _amount,
            stakeInfo.lastUpdateTs + stakeInfo.term - blockTimestamp
        );
    }
```
`stakeInfo.term` of `stakes[msg.sender][_stakeId]` would be updated in function `upgradeStake()` at line 169, which could let a user withdraw his/her shares without penalty before the term ends.

Let's say a user calls function `deposit()` to deposit some tokens at `startTs == 1` with `term == 100`.

Then at `timestamp == 60`, the user calls function `upgradeStake()`, `stakeInfo.term` would be updated to `1 + 100 - 60 == 51`. Which means the user can immediately withdraw his/her deposit without penalty! This is because `if (stakeTs + term <= blockTimestamp)` and `if (stakeTs + term + WEEK > blockTimestamp)`, function `_getPenalty()` would return 0.

```solidity=303
    function _getPenalty(
        address _user,
        uint256 _reward,
        uint256 _stakeId
    ) internal view returns (uint256) {
        uint256 depositAmount = stakes[_user][_stakeId].amount;
        uint32 term = stakes[_user][_stakeId].term;
        uint32 stakeTs = stakes[_user][_stakeId].startTs;
        uint32 blockTimestamp = uint32(block.timestamp);
        if (stakeTs + term <= blockTimestamp) {
            if (stakeTs + term + WEEK > blockTimestamp) return 0;
            uint256 lateWeeks = (blockTimestamp - (stakeTs + term)) / WEEK;
            if (lateWeeks >= MAX_PENALTY_DURATION) return _reward;
            return
                (_reward * PENALTY_PERCENT_PER_WEEK * lateWeeks) / percentBase;
        }
        return
            ((depositAmount + _reward) * (term - (blockTimestamp - stakeTs))) /
            term;
    }
```

Stake Term Changed in Function `upgradeStake()`

```solidity=108
    function setDistributionAddresses(
        address[3] calldata _newDistributionAddresses
    ) external onlyOwner {
        distributionAddresses = _newDistributionAddresses;
    }
```
Array `distributionAddresses` is updatable， while the array `distributionPercents` standing for the rates of penalty to distribute to the corresponding addresses is not.

Unchangeable Array `distributionPercents`

The return values of the transfer()/transferFrom() function calls in contract `CarpeDiem` are not checked:
- `withdraw()`
- `distributePenalty()`
- `_buyShares()`

Unchecked ERC-20 `transfer()`/`transferFrom()` Function Calls

```solidity=204
    function removeDeadStake(address _user, uint256 _stakeId) external {
        require(_stakeId < stakes[_user].length, "noSuchStake");
        StakeInfo memory stakeInfo = stakes[_user][_stakeId];
        require(stakeInfo.amount > 0, "stakeWithdrawn");
        require(
            uint32(block.timestamp) >= stakeInfo.startTs + stakeInfo.duration + 365 days,
            "stakeAlive"
        );

        _changeSharesPrice(
            stakes[_user][_stakeId].amount,
            stakes[_user][_stakeId].shares
        );
        totalShares -= (
            stakeInfo.shares + stakeInfo.bBonusShares + stakeInfo.lBonusShares
        );
        if (totalShares == 0) {
            lambda = 0;
        }
        delete stakes[_user][_stakeId];
        token.safeTransfer(_user, stakeInfo.amount);
        emit StakeRemoved(_user, _stakeId, stakeInfo.amount);
    }
```

```solidity=173
    function withdraw(uint256 _stakeId) external {
        require(_stakeId < stakes[msg.sender].length, "no such stake id");
        StakeInfo memory stakeInfo = stakes[msg.sender][_stakeId];
        require(stakeInfo.amount > 0, "stake was deleted");
        uint256 reward = getReward(msg.sender, _stakeId);
        uint256 penalty = _getPenalty(msg.sender, reward, _stakeId);
        _changeSharesPrice(
            stakeInfo.amount + reward - penalty,
            stakeInfo.shares
        );
        commissionAccumulator +=
            (penalty * (PERCENT_BASE - stakersPercent)) /
            PERCENT_BASE;
        totalShares =
            totalShares -
            stakeInfo.shares -
            stakeInfo.bBonusShares -
            stakeInfo.lBonusShares;
        if (totalShares == 0) {
            lambda = 0;
        } else {
            lambda +=
                (penalty * MULTIPLIER * stakersPercent) /
                PERCENT_BASE /
                totalShares;
        }
        delete stakes[msg.sender][_stakeId];
        token.safeTransfer(msg.sender, stakeInfo.amount + reward - penalty);
        emit Withdraw(msg.sender, _stakeId, stakeInfo.amount, reward, penalty);
    }
```
Penalty is not collected in function `removeDeadStake()`.

To compare, penalty is computed and ready to be distributed to other stakers and contract managers in function `withdraw()`.

Penalty Not Collected in Function `removeDeadStake()`

The role `_owner` of contract `CarpediemFactory` has authority over the functions below:
- `CarpediemFactory.createPool()`
- `CarpeDiem.setDistributionAddresses()`

Any compromise to the `_owner` account may allow the hacker to take advantage of this authority and exploit the commission tokens.

Centralization Risks

CarpeDiemSavings

CarpediemFactory.sol

Carpediem.sol

Carpediem_updated.sol

Carpe Diem 

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Carpe Diem

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