Billions Token - Billions

1. INTRODUCTION

Billions engaged Halborn to perform a security assessment of their smart contracts on December 5th, 2025. The assessment scope was limited to the smart contracts provided to Halborn. Commit hashes and additional details are available in the Scope section of this report.

The Billions codebase in scope consists of smart contracts implementing an upgradeable ERC20 token with ERC20Permit functionality, governed by a TimelockController with a 2-day delay, and deployed using the Transparent Proxy pattern with ProxyAdmin management.

2. ASSESSMENT SUMMARY

Halborn was allocated 1 day for this engagement and assigned 1 full-time security engineer to conduct a comprehensive review of the smart contracts within scope. The engineer is an expert in blockchain and smart contract security, with advanced skills in penetration testing and smart contract exploitation, as well as extensive knowledge of multiple blockchain protocols.

The objectives of this assessment are to:

• Identify potential security vulnerabilities within the smart contracts.

• Verify that the smart contract functionality operates as intended.

In summary, Halborn did not identify any significant security risks. However, an enhancement was recommended to improve code clarity, consistency, or maintainability, which was addressed by the Billions team:

• Lock the pragma version to the same version used during development and testing.

3. TEST APPROACH AND METHODOLODY

Halborn conducted a combination of manual code review and automated security testing to balance efficiency, timeliness, practicality, and accuracy within the scope of this assessment. While manual testing is crucial for identifying flaws in logic, processes, and implementation, automated testing enhances coverage of smart contracts and quickly detects deviations from established security best practices.

The following phases and associated tools were employed throughout the term of the assessment:

• Research into the platform's architecture, purpose and use.

• Manual code review and walkthrough of smart contracts to identify any logical issues.

• Comprehensive assessment of the safety and usage of critical Solidity variables and functions within scope that could lead to arithmetic-related vulnerabilities.

• Local testing using custom scripts (Foundry).

• Fork testing against main networks (Foundry).

• Static security analysis of scoped contracts, and imported functions (Slither).