thirdweb A-11

Security Audit

April 24th, 2023

Version 1.0.0

Presented by 0xMacro

Table of Contents


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 March 27, 2023 to April 6, 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.

Overall Assessment

The following is an aggregation of issues found by the Macro Audit team:

Severity Count Acknowledged Won't Do Addressed
Medium 2 - - 2
Code Quality 5 1 - 4
Gas Optimization 1 - - 1

thirdweb was quick to respond to these issues.


Our understanding of the specification was based on the following sources:

Source Code

The following source code was reviewed during the audit:

We audited the following PackVRF contracts within this repository:

Contract SHA256






We audited the following ExtensionRegistry contracts within this repository:

Contract SHA256






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.

Issue Descriptions and Recommendations

Click on an issue to jump to it, or scroll down to see them all.

Security Level Reference

We quantify issues in three parts:

  1. The high/medium/low/spec-breaking impact of the issue:
    • How bad things can get (for a vulnerability)
    • The significance of an improvement (for a code quality issue)
    • The amount of gas saved (for a gas optimization)
  2. The high/medium/low likelihood of the issue:
    • How likely is the issue to occur (for a vulnerability)
  3. The overall critical/high/medium/low severity of the issue.

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

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.

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.


Warnings and things to keep in mind when operating the protocol. No immediate action required.

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.

Issue Details


Low hardcoded REQUEST_CONFIRMATIONS can allow validators to reorganize blocks to increase their chances of receiving valuable rewards


Impact: Medium

Likelihood: Low

PackVRF contracts are planned to be supported on multiple chains. In specific, in the Polygon chain, reorgs of length greater than 3 blocks are more frequent (see here

Validators may find it profitable to reorg blocks after receiving rewards from a Pack in order to get more valuable rewards.

Remediations to Consider:

  • Increasing the request confirmations for the Polygon chain to a higher number.

Update signature requests may override more recent extension

Input Validation

Impact: Medium

Likelihood: Low

Through a valid signature of any DEFAULT_ADMIN_ROLE user, the ExtensionRegistry contract allows users to add, remove, and update extensions.

As there are no considerations for which extension implementation should be updated in the update case, a signature with a higher validityEndTimestamp can override a more recent, and potentially more secure implementation.

Remediations to Consider:

Consider including the implementation address intended to be changed in the signature payload and ensure this matches the current implementation before updating an extension with signature.


Impossible condition

code quality
Quality Impact

In PackVRFDirectLogic.sol, _claimRewards() function has the following require check:

require(isTrustedForwarder(msg.sender) || **msg.sender == address(VRF_V2_WRAPPER)** || opener == tx.origin, "!EOA");

The condition msg.sender == address(VRF_V2_WRAPPER) will never be true, since when the pack is opened by the VRF call msg.sender will equal the contract's address:

function sendRewardsIndirect(address _opener) external {
    **require(msg.sender == address(this));**

Consider removing the msg.sender == address(VRF_V2_WRAPPER) condition in the require statement.


Inherited contracts declare unnecessary __gap variable

code quality
Quality Impact

In PackVRFLogic.sol, the ERC2771ContextUpgradeable and ERC1155Upgradeable inherited contracts use an explicit storage slot pattern; this allows upgrading contracts without worrying about the variable order declaration and storage collisions. However, both of these contracts have declared a gap variable. Consider removing this declaration.

Response by thirdweb

Acknowledged. Not fixing at the moment.


ExtensionRegistry does not support ERC165

code quality
Quality Impact

ExtensionRegistry.sol imports the ERC165.sol contract but doesn’t inherits from it.


Unused import

code quality
Quality Impact

ExtensionRegistry.sol contract has an unused import:

import "lib/dynamic-contracts/src/interface/IRouter.sol";

setExtensionsForContractTypeWithSig **doesn’t implement sanity checks

code quality
Quality Impact

In ExtensionRegistry.sol, the setExtensionsForContractTypeWithSig function does not implement the sanity checks setExtensionForContractType does:

require(_extensionNames.length > 0, "ExtensionRegistry: no extensions provided.");
require(bytes(_contractType).length > 0, "ExtensionRegistry: empty contract type.");

This allows an empty signature request not to revert without. Consider adding sanity checks to make signature requests with empty extensions revert.


Sanity check could revert early

gas optimization
Gas Savings

In ExtensionRegistryState.sol consider performing the implementation address(0) check before storing into state the extension’s metadata to revert earlier and save gas from invalid function executions.

data.extensions[name][nextId].metadata = _extension.metadata;

    _extension.metadata.implementation != address(0),
    "ExtensionRegistryState: adding extension without implementation."


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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.