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Security Audit
September 11, 2025
Version 1.0.0
Presented by 0xMacro
This document includes the results of the security audit for towns's smart contract code as found in the section titled ‘Source Code’. The security audit was performed by the Macro security team from July 28 to July 29, 2025.
The purpose of this audit is to review the source code of certain towns Solidity contracts, and provide feedback on the design, architecture, and quality of the source code with an emphasis on validating the correctness and security of the software in its entirety.
Disclaimer: While Macro’s review is comprehensive and has surfaced some changes that should be made to the source code, this audit should not solely be relied upon for security, as no single audit is guaranteed to catch all possible bugs.
The following is an aggregation of issues found by the Macro Audit team:
| Severity | Count | Acknowledged | Won't Do | Addressed |
|---|---|---|---|---|
| Low | 1 | 1 | - | - |
| Code Quality | 1 | 1 | - | - |
towns was quick to respond to these issues.
Our understanding of the specification was based on the following sources:
Considered untrusted and potentially malicious. The system is designed to be defensive against users attempting to claim tokens for which they are not eligible.
conditionId, proof, etc.) to the contract functions. The contract validates these inputs against the protocol owner configuration in the drop conditions.claimWithPenalty, the user is responsible for using the correct expectedPenaltyBps. The contract verifies the expected bps against the claim condition bps match.Highly trusted. The owner is a privileged role and authorized entity that has complete administrative control over the airdrop conditions. This entity is trusted to:
setClaimConditions, addClaimCondition). This includes setting all parameters: start/end times, penalty rates, and the token to be distributed.maxClaimableSupply for all active claim conditions.Trusted core infrastructure. The DropFacet trusts the rewardsDistribution contract (set during initialization) to perform staking operations correctly.
stakeOnBehalf function. This includes correctly managing deposits, rewards, and withdrawals.DropFacet can implement its own reentrancy guard, the security model inherently trusts that the rewardsDistribution contract will not perform malicious re-entrant calls.Trusted core infrastructure. The DropFacet trusts this contract to handle the burning of points associated with a claim.
The following source code was reviewed during the audit:
0288990f2fe6972a297eb5c99a6b39f7ac119857
Specifically, we audited the following contracts within ./packages/contracts/src/ repository directory:
| Source Code | SHA256 |
|---|---|
| /airdrop/drop/DropBase.sol |
|
| /airdrop/drop/DropClaim.sol |
|
| /airdrop/drop/DropFacet.sol |
|
| /airdrop/drop/DropGroup.sol |
|
| /airdrop/drop/DropStorage.sol |
|
| /airdrop/drop/IDropFacet.sol |
|
Note: This document contains an audit solely of the Solidity contracts listed above. Specifically, the audit pertains only to the contracts themselves, and does not pertain to any other programs or scripts, including deployment scripts.
Click on an issue to jump to it, or scroll down to see them all.
We quantify issues in three parts:
This third part – the severity level – is a summary of how much consideration the client should give to fixing the issue. We assign severity according to the table of guidelines below:
| Severity | Description |
|---|---|
|
(C-x) Critical |
We recommend the client must fix the issue, no matter what, because not fixing would mean significant funds/assets WILL be lost. |
|
(H-x) High |
We recommend the client must address the issue, no matter what, because not fixing would be very bad, or some funds/assets will be lost, or the code’s behavior is against the provided spec. |
|
(M-x) Medium |
We recommend the client to seriously consider fixing the issue, as the implications of not fixing the issue are severe enough to impact the project significantly, albiet not in an existential manner. |
|
(L-x) Low |
The risk is small, unlikely, or may not relevant to the project in a meaningful way. Whether or not the project wants to develop a fix is up to the goals and needs of the project. |
|
(Q-x) Code Quality |
The issue identified does not pose any obvious risk, but fixing could improve overall code quality, on-chain composability, developer ergonomics, or even certain aspects of protocol design. |
|
(I-x) Informational |
Warnings and things to keep in mind when operating the protocol. No immediate action required. |
|
(G-x) Gas Optimizations |
The presented optimization suggestion would save an amount of gas significant enough, in our opinion, to be worth the development cost of implementing it. |
conditionId
In DropClaim contract, the function createLeaf() currently excludes the conditionId parameter. This means a proof is not cryptographically tied to a specific claim condition. If two different claim conditions were to accidentally have the same Merkle root, a user's proof will be valid for both.
function createLeaf(Claim calldata claim) internal pure returns (bytes32 leaf) {
address account = claim.account;
uint256 quantity = claim.quantity;
uint256 points = claim.points;
assembly ("memory-safe") {
let fmp := mload(0x40)
mstore(0, account)
mstore(0x20, quantity)
mstore(0x40, points)
leaf := keccak256(0, 0x60)
mstore(0, leaf)
leaf := keccak256(0, 0x20)
mstore(0x40, fmp)
}
}
Because claims are tracked by groupId in the supplyClaimedByWallet mapping, this would allow users to make multiple claims. Although the protocol owner must set the same root multiple times, and it’s assumed that this trusted entity will set proper values, this leaves a limited replay vector that could enable token draining.
Consider including the conditionId in the leaf generation.
Consider implementing a view function to fetch available active conditions to help interoperability with off-chain components.
Suggested draft code:
function _getActiveClaimConditions()
internal
view
returns (DropGroup.ClaimCondition[] memory activeConditions)
{
(uint48 conditionStartId, uint48 conditionCount) = _getStartIdAndCount();
if (conditionCount == 0) {
DropFacet__NoActiveClaimCondition.selector.revertWith();
}
activeConditions = new DropGroup.ClaimCondition[](conditionCount);
uint256 activeIndex;
for (uint256 i; i < conditionCount; ++i) {
DropGroup.ClaimCondition storage condition =
_getClaimConditionById(conditionStartId + i);
uint256 endTimestamp = condition.endTimestamp;
if (
block.timestamp >= condition.startTimestamp &&
(endTimestamp == 0
| block.timestamp < endTimestamp)
) {
// Add the active condition to the array and increment the index
activeConditions[activeIndex] = condition;
activeIndex++;
}
}
if (activeIndex == 0) {
DropFacet__NoActiveClaimCondition.selector.revertWith();
}
// Truncate the array to the actual number of active conditions
assembly {
mstore(activeConditions, activeIndex)
}
}
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The scope of this report and review is limited to a review of only the code presented by the towns team and only the source code Macro notes as being within the scope of Macro’s review within this report. This report does not include an audit of the deployment scripts used to deploy the Solidity contracts in the repository corresponding to this audit. Specifically, for the avoidance of doubt, this report does not constitute investment advice, is not intended to be relied upon as investment advice, is not an endorsement of this project or team, and it is not a guarantee as to the absolute security of the project. In this report you may through hypertext or other computer links, gain access to websites operated by persons other than Macro. Such hyperlinks are provided for your reference and convenience only, and are the exclusive responsibility of such websites’ owners. You agree that Macro is not responsible for the content or operation of such websites, and that Macro shall have no liability to your or any other person or entity for the use of third party websites. Macro assumes no responsibility for the use of third party software and shall have no liability whatsoever to any person or entity for the accuracy or completeness of any outcome generated by such software.