Skip to main content

Smart Contract Audit

img alt


CoinFabrik was asked to audit the contracts for the BankX project. First we will provide a summary of our discoveries, and then we will show the details of our findings.


The audited files are from the git repository located at git repository, commit
e99ff5f8cfe5697f2ddae7b1eb90cc3176659cf4, and in the git repository, commit

The audited files are:

  • BankX/contracts/BankX/BankXToken.sol: Staking token implementation
  • BankX/contracts/BankX/BankX_premint.sol: Wrapper to BankXToken
  • BankX/contracts/XSD/Pools/XSDWETHpool.sol: XSD/WETH pool
  • BankX/contracts/XSD/Pools/BankXWETHpool.sol: BankX/WETH pool
  • BankX/contracts/ERC20/ERC20Custom.sol: Modified ERC20 contract
  • BankX/contracts/XSD/Pools/CollateralPool.sol: Collateral pool
  • BankX/contracts/XSD/Pools/CollateralPoolLibrary.sol: Pool utility functions
  • CD/contracts/interfaces/BankXInterface.sol: Interface to BankX Token
  • CD/contracts/CD.sol: Certificate of Deposit main contract
  • CD/contracts/GlobalsAndUtility.sol: Utility functions and global variables
  • CD/contracts/StakeableToken.sol: Staking logic

The scope of the audit is limited to those files. No other files in this repository were audited. Its dependencies are assumed to work according to their documentation. Also, no tests were reviewed for this audit.


Without being limited to them, the audit process included the following analyses:

  • Arithmetic errors
  • Outdated version of Solidity compiler
  • Race conditions
  • Reentrancy attacks
  • Misuse of block timestamps
  • Denial of service attacks
  • Excessive gas usage
  • Missing or misused function qualifiers
  • Needlessly complex code and contract interactions
  • Poor or nonexistent error handling
  • Insufficient validation of the input parameters
  • Incorrect handling of cryptographic signatures
  • Centralization and upgradeability

Summary of Findings​

We found a critical issue, a medium issue and a minor issue. Also, several enhancements were proposed.

Security Issues​

ID Title Severity Status
CR-01 Manipulation of Daily Payout Critical Acknowledged
ME-01 Solidity Compiler Version Medium Resolved
MI-01 Hardcoded Interest Rate And Launch Time Minor Resolved

Summary of Findings​

Severity Classification​

Security risks are classified as follows:

Critical: These are issues that we manage to exploit. They compromise the system seriously. They must be fixed immediately .

Medium: These are potentially exploitable issues. Even though we did not manage to exploit them or their impact is not clear, they might represent a security risk in the near future. We suggest fixing them as soon as possible.
Minor: These issues represent problems that are relatively small or difficult to take advantage of, but can be exploited in combination with other issues. These kinds of issues do not block deployments in production environments. They should be taken into account and be fixed when possible.

Issues Status​

An issue detected by this audit can have four distinct statuses:

  • Unresolved The issue has not been resolved.
  • Acknowledged The issue remains in the code, but is a result of an intentional decision.
  • Resolved Adjusted program implementation to eliminate the risk.
  • Partially resolved: Adjusted program implementation to eliminate part of the risk. The other part remains in the code, but is a result of an intentional decision.
  • Mitigated Implemented actions to minimize the impact or likelihood of the risk

Critical Severity Issues​

CR-01 Manipulation of Daily Payout


  • contracts/GlobalsAndUtility.sol:495 (CD)

The dailyDataUpdate() calculates the daily payout taking in account the BankX token total supply amount:

rs._allocSupplyCached = bankXContract.totalSupply() + g._lockedXsTotal;

And then at _dailyRoundCalc(), line 471

rs._payoutTotal = rs._allocSupplyCached * 10000 / 171779836;

And then at _dailyRoundCalcAndStore(), line 483:

dailyData[day].dayPayoutTotal = uint72(rs._payoutTotal);

But the bankX supply can be manipulated by any authorized pool, In this way the daily payout can be manipulated, by increasing or decreasing the supply of BankX tokens and calling dailyDataUpdate() at appropriate times.


Restrict the dailyDataUpdate() function so the payout cannot be manipulated by an external entity


Acknowledged. According to the development team, this issue will be mitigated because after launch, admin keys will be renounced.

Medium Severity Issues​

ME-01 Solidity Compiler Version​

All the audited files use the statement:

pragma solidity 0.5.13;

This causes that very old solidity compiler version being used which may lead into hitting already fixed bugs. Normally this issue is of minor severity but due to the age of the solidity compiler specified (0.5.13) and the amount of bug fixes accumulated since that version, it was upgraded to Medium severity.


It is better to lock to a specific compiler version (for example, pragma solidity 0.8.13;) and keep it up to date, fully testing on each upgrade.



Minor Severity Issues​

MI-01 Hardcoded Interest Rate And Launch Time


  • contracts/GlobalsAndUtility.sol:103,471 (CD)

The Launch date is hardcoded:

uint256 internal constant LAUNCH_TIME = 1575331200;

Also, the interest rate used to calculate the daily payout is a hard-coded constant:

rs._payoutTotal = rs._allocSupplyCached * 10000 / 171779836


The LAUNCH_TIME constant could be a variable initialized at contract initialization. Also, a mechanism to update the interest rate should be implemented.




These items do not represent a security risk. They are best practices that we suggest implementing.


EN-01SafeMath Not Needed in Solidity >=0.8Implemented
EN-02Lack of Zero-Address VerificationImplemented
EN-03Different Reentrancy-Guard MethodsImplemented


EN-01 SafeMath not needed in Solidity >=0.8


  • contracts/BankXToken.sol:2
  • contracts/BankX_premint.sol:2

Solidity version 0.8 and over automatically reverts on integer overflows, not needing the SafeMath.sol contract anymore.


Remove the SafeMath.sol contract from the imports section and refactor the code appropriately.



EN-02 Lack of zero-address Verification


  • contracts/BankXWETHpool.sol:223

A zero-check on the new address should be added to the function




EN-03 Different Reentrancy-Guard Methods


  • contracts/CollateralPool.sol:69

CollateralPool.sol uses a custom lock, while XSDWETHpoo.sol and BankXWETHpool.sol uses OpenZepellins’s reentrancy guards, which is a better approach.


Replace custom guard code for OpenZepellins’s reentrancy guards



Other Considerations​

Arbitrary Bonus Creation​

  • contracts/NFTBonus.sol:22 (CD)

Any user can get an arbitrarily big bonus by setting any number of OwnerIDs using NFTBonus.sol:setOwnerIds(). The function stackStartBonusXs() then will return an arbitrarily big bonus using this operation:

return bonusXs + bonusXs * nftBonusContract.getNftsCount(msg.sender) / 10;

Here, the getNftsCount(msg.sender) can return a multiplier controlled by the attacker, so bonusXs can be arbitrarily big. This is a critical bug as it allows stealing

tokens from the contract but as this contract was out-of-scope for this audit, it was not added to the list of security issues, however it’s documented in this section.


Restrict the NFTBonus contract so only the owner can add or remove NFT ids.


BankX responded that this was a test contract and because of that, it has no security impact.


The contracts Pools/XSDWETHpool.sol, Pools/BankXWETHpool.sol and others use the Chainlink service as the price oracle.

Using an average or a backup Oracle solution might mitigate centralization, but are more costly, and security of a multi-oracle solution is not guaranteed.

Oracles are complex and approaches to decentralize come with security, accuracy and reliability tradeoffs. Chainlink oracles are powered by independent, professional and decentralized node operators that use multiple layers of aggregation -


This is not a security issue and it doesn't require a modification. It's just an observation about using a single Oracle vs using an average or a backup Oracle, solutions that improves security and mitigates centralization, but are more complex and costly. For more information about Oracle manipulation and implementation best-practices visit this article:


No upgrade mechanism exists in any contract audited.

Privileged Roles​

These are the privileged roles that we identified on each of the audited contracts.



The Owner can: Set the pool, set the Timelock address, set the Treasure address, set the XSD token address.


The Timelock address can: Set the pool, set the Timelock address, set the Treasure address, set the XSD token address


The XSD pools can: Mint new BankX tokens, burn BankX tokens. BankX/contracts/BankX/BankX_premint.sol


The Owner can: Set the BankX token address, set the XSD token address. BankX/contracts/XSD/Pools/BankXWETHpool.sol


The Owner can: Initialize the contract, change the owner address. BankX/contracts/XSD/Pools/CollateralPool.sol


The Owner can: Initialize the contract, change the owner address


The Treasury address can: Add new liquidity Tokens, add liquidity ETHs. CD/contracts/GlobalsAndUtility.sol


The Owner can: Set the BankX contract address, set the NFTBonus contract address


Disclaimer: This audit report is not a security warranty, investment advice, or an approval of the BankX project since CoinFabrik has not reviewed its platform. Moreover, it does not provide a smart contract code faultlessness guarantee.