Introduction
We express our gratitude to the Extsy team for the collaborative engagement that enabled the execution of this Smart Contract Security Assessment.
Extsy introduces XTSY, a capped ERC20 token designed for distribution across ecosystem functions such as pre-sales, staking, and treasury operations.
Document | |
|---|---|
| Name | Smart Contract Code Review and Security Analysis Report for Extsy |
| Audited By | |
| Approved By | |
| Website | https://extsy.com→ |
| Changelog | 09/09/2025 - Preliminary Report |
| 11/09/2025 - Final Report | |
| Platform | Ethereum |
| Language | Solidity |
| Tags | ERC20 |
| Methodology | https://hackenio.cc/sc_methodology→ |
Document
- Name
- Smart Contract Code Review and Security Analysis Report for Extsy
- Audited By
- Approved By
- Website
- https://extsy.com→
- Changelog
- 09/09/2025 - Preliminary Report
- 11/09/2025 - Final Report
- Platform
- Ethereum
- Language
- Solidity
- Tags
- ERC20
- Methodology
- https://hackenio.cc/sc_methodology→
Review Scope | |
|---|---|
| Repository | https://github.com/UAB-Extsy/xtsy-token-contract/→ |
| Commit | e3e3e82 |
| Final Commit | 432eaf1 |
Review Scope
- Commit
- e3e3e82
- Final Commit
- 432eaf1
Audit Summary
The system users should acknowledge all the risks summed up in the risks section of the report
Documentation quality
Functional requirements are detailed.
The project overview is detailed
All roles in the system are described.
Use cases are described and detailed.
For each contract, all futures are described.
All interactions are described.
The technical description is detailed.
Run instructions are provided.
Technical specification is provided.
The NatSpec documentation is sufficient.
Code quality
The development environment is configured.
System Overview
ExtsyToken is a capped ERC20 token designed for distribution across various ecosystem functions, including pre-sales, staking, and treasury operations. Minted at deployment, the full supply of 500 million XTSY tokens is allocated proportionally to key protocol stakeholders to ensure transparent and fixed tokenomics.
The contract uses OpenZeppelin’s audited components (ERC20Capped, ERC20Burnable) to enforce a hard supply cap, and burning functionality.
XTSY tokens are non-mintable post-deployment, with the total supply distributed at launch. Each allocation address receives a predefined percentage of the supply, supporting strategic protocol goals like liquidity provisioning, marketing, staking incentives, and ecosystem expansion.
Key Properties:
Token name: XTSY
Token symbol: XTSY
Max supply: 500,000,000 XTSY (hard capped)
Decimals: 18
Standard: ERC20
Privileged roles
EsyToken.sol:
There are no minting or administrative roles outside of the constructor; ExtsyToken is a fully minted, fixed-supply token.
Potential Risks
Scope Definition and Security Guarantees: The audit does not cover all code in the repository. Contracts outside the audit scope may introduce vulnerabilities, impacting the overall security due to the interconnected nature of smart contracts.
Centralized Token Custody at Deployment: All tokens are minted and distributed to predefined addresses at deployment without on-chain safeguards such as vesting or timelocks. This creates a centralized custody risk, where compromise of any recipient address could lead to irreversible loss or misuse of funds.
Absence of Enforced Vesting for Allocations Labeled as Vested: The documentation states that certain allocations, such as the team’s "should be vested", but the contract does not implement or enforce any vesting logic. Since recipient addresses are externally provided and receive full balances at deployment, there is no on-chain guarantee that vesting will occur as described, leaving verification dependent on post-deployment operations.
Findings
Code ― | Title | Status | Severity | |
|---|---|---|---|---|
| F-2025-1275 | Token Allocation Discrepancy Between Codebase and Documentation | fixed | Medium | |
| F-2025-1274 | Redundant Imports in ExtsyToken Contract | fixed | Observation |
Appendix 1. Definitions
Severities
When auditing smart contracts, Hacken is using a risk-based approach that considers Likelihood, Impact, Exploitability and Complexity metrics to evaluate findings and score severities.
Reference on how risk scoring is done is available through the repository in our Github organization:
Severity | Description |
|---|---|
Critical | Critical vulnerabilities are usually straightforward to exploit and can lead to the loss of user funds or contract state manipulation. |
High | High vulnerabilities are usually harder to exploit, requiring specific conditions, or have a more limited scope, but can still lead to the loss of user funds or contract state manipulation. |
Medium | Medium vulnerabilities are usually limited to state manipulations and, in most cases, cannot lead to asset loss. Contradictions and requirements violations. Major deviations from best practices are also in this category. |
Low | Major deviations from best practices or major Gas inefficiency. These issues will not have a significant impact on code execution. |
Severity
- Critical
Description
- Critical vulnerabilities are usually straightforward to exploit and can lead to the loss of user funds or contract state manipulation.
Severity
- High
Description
- High vulnerabilities are usually harder to exploit, requiring specific conditions, or have a more limited scope, but can still lead to the loss of user funds or contract state manipulation.
Severity
- Medium
Description
- Medium vulnerabilities are usually limited to state manipulations and, in most cases, cannot lead to asset loss. Contradictions and requirements violations. Major deviations from best practices are also in this category.
Severity
- Low
Description
- Major deviations from best practices or major Gas inefficiency. These issues will not have a significant impact on code execution.
Potential Risks
The "Potential Risks" section identifies issues that are not direct security vulnerabilities but could still affect the project’s performance, reliability, or user trust. These risks arise from design choices, architectural decisions, or operational practices that, while not immediately exploitable, may lead to problems under certain conditions. Additionally, potential risks can impact the quality of the audit itself, as they may involve external factors or components beyond the scope of the audit, leading to incomplete assessments or oversight of key areas. This section aims to provide a broader perspective on factors that could affect the project's long-term security, functionality, and the comprehensiveness of the audit findings.
Appendix 2. Scope
The scope of the project includes the following smart contracts from the provided repository:
Scope Details | |
|---|---|
| Repository | https://github.com/UAB-Extsy/xtsy-token-contract/→ |
| Commit | e3e3e82623a44d55b7edb9fc30484ec07414db83 |
| Final Commit | 432eaf1a9cbc4839ad18cbcc0357866067b24ad2 |
| Whitepaper | XTSY Token WP.pdf |
| Requirements | TOKENOMICS_IMPLEMENTATION.md→ |
| Technical Requirements | TOKENOMICS_IMPLEMENTATION.md→ |
Scope Details
- Commit
- e3e3e82623a44d55b7edb9fc30484ec07414db83
- Final Commit
- 432eaf1a9cbc4839ad18cbcc0357866067b24ad2
- Whitepaper
- XTSY Token WP.pdf
- Requirements
- TOKENOMICS_IMPLEMENTATION.md→
- Technical Requirements
- TOKENOMICS_IMPLEMENTATION.md→
Assets in Scope
Appendix 3. Additional Valuables
Additional Recommendations
The smart contracts in the scope of this audit could benefit from the introduction of automatic emergency actions for critical activities, such as unauthorized operations like ownership changes or proxy upgrades, as well as unexpected fund manipulations, including large withdrawals or minting events. Adding such mechanisms would enable the protocol to react automatically to unusual activity, ensuring that the contract remains secure and functions as intended.
To improve functionality, these emergency actions could be designed to trigger under specific conditions, such as:
Detecting changes to ownership or critical permissions.
Monitoring large or unexpected transactions and minting events.
Pausing operations when irregularities are identified.
These enhancements would provide an added layer of security, making the contract more robust and better equipped to handle unexpected situations while maintaining smooth operations.