Submission Details
Severity:
Users Can Match With Multiple People at Once
Summary
The dating app lets users who are already matched keep liking and matching with other people. This breaks the app's promise of "meaningful matches" since users can have many matches at the same time.
Vulnerability Details
function likeUser(address liked) external payable {
require(msg.value >= 1 ether, "Must send at least 1 ETH");
require(!likes[msg.sender][liked], "Already liked");
// No check if sender is already matched
// No check if liked person is already matched
likes[msg.sender][liked] = true;
if (likes[liked][msg.sender]) {
// Creates new match even if users are matched with others
matches[msg.sender].push(liked);
matches[liked].push(msg.sender);
matchRewards(liked, msg.sender);
}
}
Impact
Match funds get split between different matches
Users can match with many people at once
Breaks the "one meaningful match" idea
Recommendations
contract LikeRegistry {
+ uint256 public constant MAX_ACTIVE_MATCHES = 1;
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");
+ // Check if either user is already in a match
+ require(matches[msg.sender].length == 0, "Already in a match");
+ require(matches[liked].length == 0, "Target already matched");
likes[msg.sender][liked] = true;
emit Liked(msg.sender, liked);
if (likes[liked][msg.sender]) {
matches[msg.sender].push(liked);
matches[liked].push(msg.sender);
emit Matched(msg.sender, liked);
matchRewards(liked, msg.sender);
}
}
}
Rewards breakdown
nSLOC
197This contest has a flat reward structure with the following payouts:
100 EXP
20 EXP
2 EXP
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