Prepared by:
HALBORN
Last Updated 04/18/2025
Date of Engagement: February 26th, 2025 - February 28th, 2025
100% of all REPORTED Findings have been addressed
All findings
18
Critical
0
High
0
Medium
2
Low
5
Informational
11
Fan.Fun engaged Halborn to conduct a security assessment of their Fandotfun project beginning on February 27th and ending on March 3rd. The security assessment was scoped to the smart contract provided in the GitHub repository. Commit hash and further details can be found in the Scope section of this report.
FanDotFun is a decentralized protocol for creator-fan engagement through time-decaying keys.
Halborn was provided 3 days for the engagement and assigned one full-time security engineer to review the security of the smart contract in scope. The engineer is a blockchain and smart contract security expert with advanced penetration testing and smart contract hacking skills, and deep knowledge of multiple blockchain protocols.
The purpose of the assessment is to:
Identify potential security issues within the smart contract.
Ensure that smart contract functionality operates as intended.
In summary, Halborn identified some improvements to reduce the likelihood and impact of risks, which were partially addressed by the Fan.Fun team. The main ones were the following:
Implement Slippage Protection and/or return excess funds sent by subscribers.
Consider adopting a pull pattern for claiming decayed keys.
Review fee calculations in claim() or prevent protocol fees from being 0.
Halborn performed a combination of manual and automated security testing to balance efficiency, timeliness, practicality, and accuracy in regard to the scope of this assessment. While manual testing is recommended to uncover flaws in logic, process, and implementation; automated testing techniques help enhance coverage of the code and can quickly identify items that do not follow the security best practices. The following phases and associated tools were used during the assessment:
Research into architecture and purpose.
Smart contract manual code review and walkthrough.
Graphing out functionality and contract logic/connectivity/functions (solgraph).
Manual assessment of use and safety for the critical Solidity variables and functions in scope to identify any arithmetic related vulnerability classes.
Manual testing by custom scripts.
Static Analysis of security for scoped contract, and imported functions (slither).
| EXPLOITABILITY METRIC () | METRIC VALUE | NUMERICAL VALUE |
|---|---|---|
| Attack Origin (AO) | Arbitrary (AO:A) Specific (AO:S) | 1 0.2 |
| Attack Cost (AC) | Low (AC:L) Medium (AC:M) High (AC:H) | 1 0.67 0.33 |
| Attack Complexity (AX) | Low (AX:L) Medium (AX:M) High (AX:H) | 1 0.67 0.33 |
| IMPACT METRIC () | METRIC VALUE | NUMERICAL VALUE |
|---|---|---|
| Confidentiality (C) | None (C:N) Low (C:L) Medium (C:M) High (C:H) Critical (C:C) | 0 0.25 0.5 0.75 1 |
| Integrity (I) | None (I:N) Low (I:L) Medium (I:M) High (I:H) Critical (I:C) | 0 0.25 0.5 0.75 1 |
| Availability (A) | None (A:N) Low (A:L) Medium (A:M) High (A:H) Critical (A:C) | 0 0.25 0.5 0.75 1 |
| Deposit (D) | None (D:N) Low (D:L) Medium (D:M) High (D:H) Critical (D:C) | 0 0.25 0.5 0.75 1 |
| Yield (Y) | None (Y:N) Low (Y:L) Medium (Y:M) High (Y:H) Critical (Y:C) | 0 0.25 0.5 0.75 1 |
| SEVERITY COEFFICIENT () | COEFFICIENT VALUE | NUMERICAL VALUE |
|---|---|---|
| Reversibility () | None (R:N) Partial (R:P) Full (R:F) | 1 0.5 0.25 |
| Scope () | Changed (S:C) Unchanged (S:U) | 1.25 1 |
| Severity | Score Value Range |
|---|---|
| Critical | 9 - 10 |
| High | 7 - 8.9 |
| Medium | 4.5 - 6.9 |
| Low | 2 - 4.4 |
| Informational | 0 - 1.9 |
Critical
0
High
0
Medium
2
Low
5
Informational
11
| Security analysis | Risk level | Remediation Date |
|---|---|---|
| Front-Running Risks: Potential DoS, Sandwich Attacks, and Slippage in Buy/Sell | Medium | Solved - 03/06/2025 |
| Creators Could Prevent Their Subscribers From Claiming | Medium | Risk Accepted - 03/10/2025 |
| Protocol Cannot Have 0% Fees Due to Adjusted Calculation in Claim() | Low | Risk Accepted - 03/10/2025 |
| Malicious Subscribers Could Potentially DoS Claims | Low | Risk Accepted - 03/10/2025 |
| Missing Emergency Withdrawal Capability | Low | Solved - 03/06/2025 |
| Missing Pausing Mechanism | Low | Risk Accepted - 03/10/2025 |
| Centralization Risks | Low | Risk Accepted - 03/10/2025 |
| Subscribers Can Buy Zero Keys | Informational | Acknowledged - 03/10/2025 |
| Single-step Ownership Transfer Process | Informational | Acknowledged - 03/10/2025 |
| Owner Can Renounce Ownership | Informational | Acknowledged - 03/10/2025 |
| Missing Visibility Attribute | Informational | Solved - 03/07/2025 |
| Lack of Event Emission | Informational | Solved - 03/06/2025 |
| Magic Numbers in Use | Informational | Solved - 03/07/2025 |
| Style Guide Optimizations | Informational | Solved - 03/07/2025 |
| Events Missing Indexed Fields | Informational | Acknowledged - 03/10/2025 |
| Incomplete NatSpec Documentation | Informational | Solved - 03/07/2025 |
| Missing Input Validation | Informational | Acknowledged - 03/10/2025 |
| Inconsistent License Declarations | Informational | Solved - 03/07/2025 |
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Halborn strongly recommends conducting a follow-up assessment of the project either within six months or immediately following any material changes to the codebase, whichever comes first. This approach is crucial for maintaining the project’s integrity and addressing potential vulnerabilities introduced by code modifications.
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