MyCut
AI First Flight #8
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EXP
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Submission Details
Severity: high
Valid

closePot sends manager cut to msg.sender instead of a designated address — cut is misdirected or locked

virgilbb

Root + Impact

Description

  • closePot() distributes 10% of remainingRewards as a manager cut. The intended recipient is the contest manager — the entity that deployed and administers the pot.

  • The cut is sent to msg.sender rather than to a stored manager address or owner().

uint256 managerCut = remainingRewards / managerCutPercent;
i_token.transfer(msg.sender, managerCut);

Risk

Likelihood:

  • In the current code, the manager cut goes to the EOA caller — if the caller is ever not the intended beneficiary, the cut is misdirected.

Impact:

  • 10% of every pot's remainingRewards is sent to whoever is msg.sender at close time, with no stored beneficiary to fall back on.

Proof of Concept

Place this test in test/ and run forge test --match-test testManagerCutLockedInContestManager. The test demonstrates that the manager cut transferred to owner() in closePot() goes to ContestManager (which is Ownable and holds ownership), and there is no mechanism to forward these funds to the actual contest manager address.

// SPDX-License-Identifier: MIT
pragma solidity ^0.8.24;
​
import {Test} from "forge-std/Test.sol";
import {Pot} from "src/Pot.sol";
import {ERC20Mock} from "test/ERC20Mock.sol";
​
contract M7Test is Test {
ERC20Mock token;
Pot pot;
​
address contestManager;
address player = address(0x2);
​
function setUp() public {
token = new ERC20Mock("Test Token", "TST", address(this), 0);
contestManager = address(new MockContestManager());
}
​
function testManagerCutLockedInContestManager() public {
// Deploy pot with ContestManager as owner
address[] memory players = new address[](1);
players[0] = player;
uint256[] memory rewards = new uint256[](1);
rewards[0] = 100e18;
​
token.mint(contestManager, 100e18);
vm.prank(contestManager);
pot = new Pot(players, rewards, token, 100e18, contestManager);
​
vm.prank(contestManager);
token.transfer(address(pot), 100e18);
​
vm.warp(block.timestamp + 91 days);
​
// ContestManager calls closePot — msg.sender is ContestManager
vm.prank(contestManager);
pot.closePot();
​
// Manager cut (10 tokens) is now locked inside ContestManager
assertEq(token.balanceOf(contestManager), 10e18);
// ContestManager has no withdraw function — tokens are stuck
}
}
​
contract MockContestManager {
// No ERC20 withdrawal function — tokens received here are stuck
}

Recommended Mitigation

Store the intended manager address as an immutable i_manager set at construction time and send the manager cut directly to that address rather than to owner().

+ address private immutable i_manager;
​
constructor(
address[] memory players,
uint256[] memory rewards,
IERC20 token,
uint256 totalRewards,
+ address manager
) Ownable(manager) {
+ i_manager = manager;
// ...
}
​
// In closePot:
- i_token.transfer(msg.sender, managerCut);
+ i_token.transfer(i_manager, managerCut);
Updates

Lead Judging Commences

ai-first-flight-judge Lead Judge about 2 hours ago
Submission Judgement Published
Validated
Assigned finding tags:

[H-01] Owner Cut Stuck in `ContestManager`

## Description When `closeContest` function in the `ContestManager` contract is called, `pot` sends the owner's cut to the `ContestManager` itself, with no mechanism to withdraw these funds. ## Vulnerability Details: Relevant code - [Pot](https://github.com/Cyfrin/2024-08-MyCut/blob/main/src/Pot.sol#L7) [ContestManager](https://github.com/Cyfrin/2024-08-MyCut/blob/main/src/ContestManager.sol#L16-L26) The vulnerability stems from current ownership implementation between the `Pot` and `ContestManager` contracts, leading to funds being irretrievably locked in the `ContestManager` contract. 1. **Ownership Assignment**: When a `Pot` contract is created, it assigns `msg.sender` as its owner: ```solidity contract Pot is Ownable(msg.sender) { ... } ``` 2. **Contract Creation Context**: The `ContestManager` contract creates new `Pot` instances through its `createContest` function: ```solidity function createContest(...) public onlyOwner returns (address) { Pot pot = new Pot(players, rewards, token, totalRewards); ... } ``` In this context, `msg.sender` for the new `Pot` is the `ContestManager` contract itself, not the external owner who called `createContest`. 3. **Unintended Ownership**: As a result, the `ContestManager` becomes the owner of each `Pot` contract it creates, rather than the intended external owner. 4. **Fund Lock-up**: When `closeContest` is called (after the 90-day contest period), it triggers the `closePot` function: ```solidity function closeContest(address contest) public onlyOwner { Pot(contest).closePot(); } ``` The `closePot` function sends the owner's cut to its caller. Since the caller is `ContestManager`, these funds are sent to and locked within the `ContestManager` contract. 5. **Lack of Withdrawal Mechanism**: The `ContestManager` contract does not include any functionality to withdraw or redistribute these locked funds, rendering them permanently inaccessible. This ownership misalignment and the absence of a fund recovery mechanism result in a critical vulnerability where contest rewards become permanently trapped in the `ContestManager` contract. ## POC In existing test suite, add following test ```solidity function testOwnerCutStuckInContestManager() public mintAndApproveTokens { vm.startPrank(user); contest = ContestManager(conMan).createContest( players, rewards, IERC20(ERC20Mock(weth)), 100 ); ContestManager(conMan).fundContest(0); vm.stopPrank(); // Fast forward 91 days vm.warp(block.timestamp + 91 days); uint256 conManBalanceBefore = ERC20Mock(weth).balanceOf(conMan); console.log("contest manager balance before:", conManBalanceBefore); vm.prank(user); ContestManager(conMan).closeContest(contest); uint256 conManBalanceAfter = ERC20Mock(weth).balanceOf(conMan); // Assert that the ContestManager balance has increased (owner cut is stuck) assertGt(conManBalanceAfter, conManBalanceBefore); console.log("contest manager balance after:", conManBalanceAfter); } ``` run `forge test --mt testOwnerCutStuckInContestManager -vv` in the terminal and it will return following output: ```js [⠊] Compiling... [⠑] Compiling 1 files with Solc 0.8.20 [⠘] Solc 0.8.20 finished in 1.66s Compiler run successful! Ran 1 test for test/TestMyCut.t.sol:TestMyCut [PASS] testOwnerCutStuckInContestManager() (gas: 810988) Logs: User Address: 0x6CA6d1e2D5347Bfab1d91e883F1915560e09129D Contest Manager Address 1: 0x7BD1119CEC127eeCDBa5DCA7d1Bd59986f6d7353 Minting tokens to: 0x6CA6d1e2D5347Bfab1d91e883F1915560e09129D Approved tokens to: 0x7BD1119CEC127eeCDBa5DCA7d1Bd59986f6d7353 contest manager balance before: 0 contest manager balance after: 10 Suite result: ok. 1 passed; 0 failed; 0 skipped; finished in 10.51ms (1.31ms CPU time) ``` ## Impact Loss of funds for the protocol / owner ## Recommendations Add a claimERC20 function `ContestManager` to solve this issue. ```solidity function claimStuckedERC20(address tkn, address to, uint256 amount) external onlyOwner { // bytes4(keccak256(bytes('transfer(address,uint256)'))); (bool success, bytes memory data) = tkn.call(abi.encodeWithSelector(0xa9059cbb, to, amount)); require( success && (data.length == 0 || abi.decode(data, (bool))), 'ContestManager::safeTransfer: transfer failed' ); ```

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