QST Staking Protocol - QuStream

1. Introduction

QuStream team engaged Halborn to conduct a security assessment of the qst-staking program from September 18th to September 25th, 2025. The security assessment was scoped to the smart contracts provided in the GitHub repository QuStream; commit hashes and further details can be found in the Scope section of this report.

qst-staking program is a secure, time-locked staking system on Solana designed to incentivize long-term commitment and network participation. Users can stake QST tokens in 25-day lock periods, during which they earn node keys (at a rate of two keys per 200,000 QST, subject to minimum requirements) and may optionally enroll in a bonus program that extends their commitment by an additional 10 days in exchange for enhanced rewards. The protocol incorporates a penalty-sharing mechanism , redistributing penalties collected from early unstakers among bonus enrollees, thereby aligning incentives and reinforcing protocol security.

It should be noted that changes made during the remediation phase that do not directly address the identified issues are considered out of scope for this security assessment.

2. Assessment Summary

Halborn was provided 6 days for the engagement and assigned 1 full-time security engineer to review the security of the Solana Program in scope. The engineer is blockchain and smart contract security expert with advanced smart contract hacking skills, and deep knowledge of multiple blockchain protocols .

The purpose of the assessment is to:

• Identify potential security issues within the Solana Program.

• Ensure that smart contract functionality operates as intended.

In summary, Halborn identified some improvements to reduce the likelihood and impact of risks, which have been addressed by the QuStream team. The main ones were the following:

• Modify the participation window and add additional validation in unstake_tokens in order to prevent unstaking until the stake window has ended.

• Decouple the withdrawal process into two distinct steps.

• Remove the ability to restart a staking window or introduce a stake_window_idstored in both pool and user stake accounts.

3. Test Approach and Methodology

Halborn performed a combination of a manual review of the source code and automated security testing to balance efficiency, timeliness, practicality, and accuracy in regard to the scope of the program assessment. While manual testing is recommended to uncover flaws in business logic, processes, and implementation; automated testing techniques help enhance coverage of programs and can quickly identify items that do not follow security best practices.

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

• Research into the architecture, purpose, and use of the platform.

• Manual program source code review to identify business logic issues.

• Mapping out possible attack vectors.

• Thorough assessment of safety and usage of critical Rust variables and functions in scope that could lead to arithmetic vulnerabilities.

• Scanning dependencies for known vulnerabilities (cargo audit).

• Local runtime testing (anchor test and <solana-test-framework).