DatingDapp
AI First Flight #6
Beginner FriendlyFoundrySolidityNFT
EXP
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Submission Details
Severity: high
Valid

H-1: Overpayment above 1 ETH is silently accepted and trapped

rubabbel

Root + Impact

likeUser only enforces a lower bound (>= 1 ether), so any excess is absorbed by the contract with no refund and no credit. Combined with the missing accounting this means the entire overpayment is permanently lost.

Description

// src/LikeRegistry.sol
function likeUser(address liked) external payable {
@> require(msg.value >= 1 ether, "Must send at least 1 ETH"); // accepts any excess
...
@> // surplus (msg.value - 1 ether) is neither refunded nor recorded
}

Risk

Likelihood: Medium — a wallet/UI sending more than 1 ETH, or a script using a computed amount.

Impact: Direct, irreversible loss of the excess ETH for the sender.

Proof of Concept

function test_OverpaymentTrapped() public {
_mint(alice);
_mint(bob);
vm.deal(alice, 10 ether);
​
vm.prank(alice);
registry.likeUser{value: 5 ether}(bob);
​
assertEq(address(registry).balance, 5 ether); // full overpayment absorbed
assertEq(registry.userBalances(alice), 0); // nothing credited/refunded
}

Recommended Mitigation

- require(msg.value >= 1 ether, "Must send at least 1 ETH");
+ require(msg.value == 1 ether, "Must send exactly 1 ETH");

Or refund the surplus:

+ if (msg.value > 1 ether) {
+ (bool ok,) = payable(msg.sender).call{value: msg.value - 1 ether}("");
+ require(ok, "Refund failed");
+ }
Updates

Lead Judging Commences

ai-first-flight-judge Lead Judge about 6 hours ago
Submission Judgement Published
Validated
Assigned finding tags:

[H-01] After the user calls the `likeUser` function, the userBalance does not increase by the corresponding value.

## Description User A calls `likeUser` and sends `value > 1` ETH. According to the design of DatingDapp, the amount for user A should be accumulated by `userBalances`. Otherwise, in the subsequent calculations, the balance for each user will be 0. ## Vulnerability Details When User A calls `likeUser`, the accumulation of `userBalances` is not performed. ```solidity function likeUser( address liked ) external payable { require(msg.value >= 1 ether, "Must send at least 1 ETH"); require(!likes[msg.sender][liked], "Already liked"); require(msg.sender != liked, "Cannot like yourself"); require(profileNFT.profileToToken(msg.sender) != 0, "Must have a profile NFT"); require(profileNFT.profileToToken(liked) != 0, "Liked user must have a profile NFT"); likes[msg.sender][liked] = true; emit Liked(msg.sender, liked); // Check if mutual like if (likes[liked][msg.sender]) { matches[msg.sender].push(liked); matches[liked].push(msg.sender); emit Matched(msg.sender, liked); matchRewards(liked, msg.sender); } } ``` This will result in `totalRewards` always being 0, affecting all subsequent calculations: ```solidity uint256 totalRewards = matchUserOne + matchUserTwo; uint256 matchingFees = (totalRewards * FIXEDFEE ) / 100; uint256 rewards = totalRewards - matchingFees; totalFees += matchingFees; ``` ## POC ```solidity function testUserBalanceshouldIncreaseAfterLike() public { vm.prank(user1); likeRegistry.likeUser{value: 20 ether}(user2); assertEq(likeRegistry.userBalances(user1), 20 ether, "User1 balance should be 20 ether"); } ``` Then we will get an error: ```shell [FAIL: User1 balance should be 20 ether: 0 != 20000000000000000000] ``` ## Impact - Users will be unable to receive rewards. - The contract owner will also be unable to withdraw ETH from the contract. ## Recommendations Add processing for `userBalances` in the `likeUser` function: ```diff function likeUser( address liked ) external payable { require(msg.value >= 1 ether, "Must send at least 1 ETH"); require(!likes[msg.sender][liked], "Already liked"); require(msg.sender != liked, "Cannot like yourself"); require(profileNFT.profileToToken(msg.sender) != 0, "Must have a profile NFT"); require(profileNFT.profileToToken(liked) != 0, "Liked user must have a profile NFT"); likes[msg.sender][liked] = true; + userBalances[msg.sender] += msg.value; emit Liked(msg.sender, liked); [...] } ```

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