June 30th, 2023
Presented by 0xMacro
This document includes the results of the security audit for thirdweb's smart contract code as found in the section titled ‘Source Code’. The security audit was performed by the Macro security team from June 13, 2023 to June 23, 2023.
The purpose of this audit is to review the source code of certain thirdweb 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:
thirdweb was quick to respond to these issues.
Our understanding of the specification was based on the following sources:
The following source code was reviewed during the audit:
We audited the following contracts specificially for the Dynamic Drops audit:
We audited the following contracts specificially for the Loyalty Card audit:
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:
We recommend the client must fix the issue, no matter what, because not fixing would mean significant funds/assets WILL be lost.
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.
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.
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.
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.
Warnings and things to keep in mind when operating the protocol. No immediate action required.
The presented optimization suggestion would save an amount of gas significant enough, in our opinion, to be worth the development cost of implementing it.
LoyaltyCard.mintWithSignature always only mints 1 NFT to the user as stated in the comments:
/// @dev Mints an NFT according to the provided mint request. Always mints 1 NFT.
and defined by the line LoyaltyCard#L276:
_collectPrice, the total price the user has to pay is calculated as follows:
uint256 totalPrice = _quantityToClaim * _pricePerToken;
Thus, for quantity > 1, the user has to pay the total price determined by the quantity, despite only getting 1 NFT minted.
Remediations to Consider
Consider only allowing mint request with quantity = 1 and otherwise revert.
DropERC20Logic inherits from
Drop contract which implements the
claim(…) function that calls
_collectPriceOnClaim to transfer payment to
The issue of locking native tokens in the contract occurs under the following circumstances:
claimConditionsis set to ERC20.
claimwith appropriate amount of ERC20 tokens approved and accidentally also passes native tokens along.
As a result, the
claim call succeeds but the native tokens passed along will be locked within the DropERC20 contract.
Note that this issue also applies to
An admin could rescue the tokens by adding a new extension that provides appropriate function to transfer tokens back to original owners. However, it is recommended to avoid such situations in the first place.
Consider checking that no native tokens are transferred (
msg.value == 0) when payment currency is set to ERC20.
LoyaltyCard inherits from
ReentrancyGuardUpgradeable but is not being initialized in the
Note that due to the logic in
ReentrancyGuardUpgradeable, this doesn’t impose any security risk, but it is considered as best practice to properly initialize all parent contracts.
Remediations to Consider
ReentrancyGuardUpgradeable properly by adding
__ReentrancyGuard_init to the
Due to the use of dynamic contract pattern and its use of unstructured storage,
__gap variables declared in some of the upgradable contracts are not needed. Consider removing the
__gap variable from the following files:
LoyaltyCard allows the transfers of NFTs by default; enabled by the following line in
Due to the use case of
LoyaltyCard - namely issuing NFTs to loyal customers - consider restricting transfers by default for normal users and only allow transfers for admins having the
OpenEditionERC721 has been recently updated to support a new fee mechanism called “flat fee” besides “percentage fee”. However, all three drop contracts only support “percentage fee”. Consider updating drop contracts to support “flat fee” in addition to “percentage fee”.
Macro makes no warranties, either express, implied, statutory, or otherwise, with respect to the services or deliverables provided in this report, and Macro specifically disclaims all implied warranties of merchantability, fitness for a particular purpose, noninfringement and those arising from a course of dealing, usage or trade with respect thereto, and all such warranties are hereby excluded to the fullest extent permitted by law.
Macro will not be liable for any lost profits, business, contracts, revenue, goodwill, production, anticipated savings, loss of data, or costs of procurement of substitute goods or services or for any claim or demand by any other party. In no event will Macro be liable for consequential, incidental, special, indirect, or exemplary damages arising out of this agreement or any work statement, however caused and (to the fullest extent permitted by law) under any theory of liability (including negligence), even if Macro has been advised of the possibility of such damages.
The scope of this report and review is limited to a review of only the code presented by the thirdweb 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.