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

Manager cut is sent to the `ContestManager` contract, which has no withdrawal function — funds permanently locked

0xki

Root + Impact

Description

  • When a `Pot` is closed after the claim period, `closePot` sends the 10% manager cut to `msg.sender`, which is expected to be the protocol owner/admin.

  • Because every Pot is deployed **by** the ContestManager (new Pot(...) inside createContest), the Pot's owner is the ContestManager contract, not the admin EOA. closePot is onlyOwner, so its msg.sender is the ContestManager. The cut is transferred to the ContestManager, which exposes **no function** to move ERC20 tokens out — the cut is locked forever.

/ src/Pot.sol
contract Pot is Ownable(msg.sender) { ... } // owner = deployer = ContestManager
​
function closePot() external onlyOwner {
if (block.timestamp - i_deployedAt < 90 days) revert Pot__StillOpenForClaim();
if (remainingRewards > 0) {
uint256 managerCut = remainingRewards / managerCutPercent;
@> i_token.transfer(msg.sender, managerCut); // msg.sender == ContestManager, no way to withdraw
...
}
}

Risk

Likelihood:

  • Occurs on **every** `closeContest` call where `remainingRewards > 0` (i.e. any contest with unclaimed rewards, which is the normal case).

  • Requires no special conditions or attacker — it is the default outcome of the intended close flow.

Impact:

  • The 10% manager cut of every contest is irretrievably locked in the `ContestManager`.

  • Across many contests these trapped funds accumulate with no recovery path (no upgrade, no admin function).

Proof of Concept

function test_H01_managerCutStuck() public mintAndApproveTokens {
address[] memory p = new address[](4);
p[0] = makeAddr("a"); p[1] = makeAddr("b"); p[2] = makeAddr("c"); p[3] = makeAddr("d");
uint256[] memory r = new uint256[](4);
r[0] = 25; r[1] = 25; r[2] = 25; r[3] = 25;
​
vm.startPrank(user);
contest = ContestManager(conMan).createContest(p, r, IERC20(ERC20Mock(weth)), 100);
ContestManager(conMan).fundContest(0);
vm.stopPrank();
​
// nobody claims -> remainingRewards = 100, managerCut = 10
vm.warp(block.timestamp + 91 days);
vm.prank(user);
ContestManager(conMan).closeContest(contest);
​
// The 10-token cut is trapped in the ContestManager; the admin EOA gets nothing.
assertEq(ERC20Mock(weth).balanceOf(conMan), 10);
assertEq(ERC20Mock(weth).balanceOf(user), STARTING_USER_BALANCE - 100);
}

Result: `[PASS]` — `balanceOf(conMan) == 10`, admin EOA received `0`. The `ContestManager` has no function capable of transferring that token out.

Recommended Mitigation

Send the cut to a real recipient instead of `msg.sender`, or add a rescue function to `ContestManager`. Preferred fix — transfer the cut to the actual owner (the admin) rather than the calling contract:

function closePot() external onlyOwner {
if (block.timestamp - i_deployedAt < 90 days) revert Pot__StillOpenForClaim();
if (remainingRewards > 0) {
uint256 managerCut = remainingRewards / managerCutPercent;
- i_token.transfer(msg.sender, managerCut);
+ i_token.transfer(Ownable(msg.sender).owner(), managerCut); // forward to the ContestManager's owner (admin)
```
​
Or add a sweep to `ContestManager`:
​
```diff
+ function withdrawToken(IERC20 token, address to, uint256 amount) external onlyOwner {
+ token.transfer(to, amount);
+ }
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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