MEDIUM severity: ELFM - Exceeds Fees Limit. The contract owner can increase fees above 25%, potentially taking advantage of it.

Vulnerable code:
/**
 * This smart contract code is Copyright 2018 WiBX. For more information see https://wibx.io
 *
 * Licensed under the Apache License, version 2.0: https://github.com/wibxcoin/Contracts/blob/master/LICENSE
 * It includes parts of OpenZeppelin, licensed under the MIT License: https://github.com/OpenZeppelin/openzeppelin-solidity/blob/master/LICENSE
 */

pragma solidity ^0.5.0;

/**
 * @title Roles
 * @dev Library for managing addresses assigned to a Role.
 */
library Roles {
    struct Role {
        mapping (address => bool) bearer;
    }

    /**
     * @dev give an account access to this role
     */
    function add(Role storage role, address account) internal {
        require(account != address(0));
        require(!has(role, account));

        role.bearer[account] = true;
    }

    /**
     * @dev remove an account's access to this role
     */
    function remove(Role storage role, address account) internal {
        require(account != address(0));
        require(has(role, account));

        role.bearer[account] = false;
    }

    /**
     * @dev check if an account has this role
     * @return bool
     */
    function has(Role storage role, address account) internal view returns (bool) {
        require(account != address(0));
        return role.bearer[account];
    }
}




/**
 * @title ERC20 interface
 * @dev see https://github.com/ethereum/EIPs/issues/20
 */
interface IERC20 {
    function transfer(address to, uint256 value) external returns (bool);

    function approve(address spender, uint256 value) external returns (bool);

    function transferFrom(address from, address to, uint256 value) external returns (bool);

    function totalSupply() external view returns (uint256);

    function balanceOf(address who) external view returns (uint256);

    function allowance(address owner, address spender) external view returns (uint256);

    event Transfer(address indexed from, address indexed to, uint256 value);

    event Approval(address indexed owner, address indexed spender, uint256 value);
}




contract PauserRole {
    using Roles for Roles.Role;

    event PauserAdded(address indexed account);
    event PauserRemoved(address indexed account);

    Roles.Role private _pausers;

    constructor () internal {
        _addPauser(msg.sender);
    }

    modifier onlyPauser() {
        require(isPauser(msg.sender));
        _;
    }

    function isPauser(address account) public view returns (bool) {
        return _pausers.has(account);
    }

    function addPauser(address account) public onlyPauser {
        _addPauser(account);
    }

    function renouncePauser() public {
        _removePauser(msg.sender);
    }

    function _addPauser(address account) internal {
        _pausers.add(account);
        emit PauserAdded(account);
    }

    function _removePauser(address account) internal {
        _pausers.remove(account);
        emit PauserRemoved(account);
    }
}


/**
 * @title SafeMath
 * @dev Unsigned math operations with safety checks that revert on error
 */
library SafeMath {
    /**
    * @dev Multiplies two unsigned integers, reverts on overflow.
    */
    function mul(uint256 a, uint256 b) internal pure returns (uint256) {
        // Gas optimization: this is cheaper than requiring 'a' not being zero, but the
        // benefit is lost if 'b' is also tested.
        // See: https://github.com/OpenZeppelin/openzeppelin-solidity/pull/522
        if (a == 0) {
            return 0;
        }

        uint256 c = a * b;
        require(c / a == b);

        return c;
    }

    /**
    * @dev Integer division of two unsigned integers truncating the quotient, reverts on division by zero.
    */
    function div(uint256 a, uint256 b) internal pure returns (uint256) {
        // Solidity only automatically asserts when dividing by 0
        require(b > 0);
        uint256 c = a / b;
        // assert(a == b * c + a % b); // There is no case in which this doesn't hold

        return c;
    }

    /**
    * @dev Subtracts two unsigned integers, reverts on overflow (i.e. if subtrahend is greater than minuend).
    */
    function sub(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b <= a);
        uint256 c = a - b;

        return c;
    }

    /**
    * @dev Adds two unsigned integers, reverts on overflow.
    */
    function add(uint256 a, uint256 b) internal pure returns (uint256) {
        uint256 c = a + b;
        require(c >= a);

        return c;
    }

    /**
    * @dev Divides two unsigned integers and returns the remainder (unsigned integer modulo),
    * reverts when dividing by zero.
    */
    function mod(uint256 a, uint256 b) internal pure returns (uint256) {
        require(b != 0);
        return a % b;
    }
}





/**
 * @title Taxation Library
 *
 * @dev Helpers for taxation
 */
library TaxLib
{
    using SafeMath for uint256;

    /**
     * Modifiable tax container
     */
    struct DynamicTax
    {
        /**
         * Tax amount per each transaction (in %).
         */
        uint256 amount;

        /**
         * The shift value.
         * Represents: 100 * 10 ** shift
         */
        uint256 shift;
    }

    /**
     * @dev Apply percentage to the value.
     *
     * @param taxAmount The amount of tax
     * @param shift The shift division amount
     * @param value The total amount
     * @return The tax amount to be payed (in WEI)
     */
    function applyTax(uint256 taxAmount, uint256 shift, uint256 value) internal pure returns (uint256)
    {
        uint256 temp = value.mul(taxAmount);

        return temp.div(shift);
    }

    /**
     * @dev Normalize the shift value
     *
     * @param shift The power chosen
     */
    function normalizeShiftAmount(uint256 shift) internal pure returns (uint256)
    {
        require(shift >= 0 && shift <= 2, "You can't set more than 2 decimal places");

        uint256 value = 100;

        return value.mul(10 ** shift);
    }
}




/**
 * @title Standard ERC20 token
 *
 * @dev Implementation of the basic standard token.
 * https://github.com/ethereum/EIPs/blob/master/EIPS/eip-20.md
 * Originally based on code by FirstBlood:
 * https://github.com/Firstbloodio/token/blob/master/smart_contract/FirstBloodToken.sol
 *
 * This implementation emits additional Approval events, allowing applications to reconstruct the allowance status for
 * all accounts just by listening to said events. Note that this isn't required by the specification, and other
 * compliant implementations may not do it.
 */
contract ERC20 is IERC20 {
    using SafeMath for uint256;

    mapping (address => uint256) private _balances;

    mapping (address => mapping (address => uint256)) private _allowed;

    uint256 private _totalSupply;

    /**
    * @dev Total number of tokens in existence
    */
    function totalSupply() public view returns (uint256) {
        return _totalSupply;
    }

    /**
    * @dev Gets the balance of the specified address.
    * @param owner The address to query the balance of.
    * @return An uint256 representing the amount owned by the passed address.
    */
    function balanceOf(address owner) public view returns (uint256) {
        return _balances[owner];
    }

    /**
     * @dev Function to check the amount of tokens that an owner allowed to a spender.
     * @param owner address The address which owns the funds.
     * @param spender address The address which will spend the funds.
     * @return A uint256 specifying the amount of tokens still available for the spender.
     */
    function allowance(address owner, address spender) public view returns (uint256) {
        return _allowed[owner][spender];
    }

    /**
    * @dev Transfer token for a specified address
    * @param to The address to transfer to.
    * @param value The amount to be transferred.
    */
    function transfer(address to, uint256 value) public returns (bool) {
        _transfer(msg.sender, to, value);
        return true;
    }

    /**
     * @dev Approve the passed address to spend the specified amount of tokens on behalf of msg.sender.
     * Beware that changing an allowance with this method brings the risk that someone may use both the old
     * and the new allowance by unfortunate transaction ordering. One possible solution to mitigate this
     * race condition is to first reduce the spender's allowance to 0 and set the desired value afterwards:
     * https://github.com/ethereum/EIPs/issues/20#issuecomment-263524729
     * @param spender The address which will spend the funds.
     * @param value The amount of tokens to be spent.
     */
    function approve(address spender, uint256 value) public returns (bool) {
        require(spender != address(0));

        _allowed[msg.sender][spender] = value;
        emit Approval(msg.sender, spender, value);
        return true;
    }

    /**
     * @dev Transfer tokens from one address to another.
     * Note that while this function emits an Approval event, this is not required as per the specification,
     * and other compliant implementations may not emit the event.
     * @param from address The address which you want to send tokens from
     * @param to address The address which you want to transfer to
     * @param value uint256 the amount of tokens to be transferred
     */
    function transferFrom(address from, address to, uint256 value) public returns (bool) {
        _allowed[from][msg.sender] = _allowed[from][msg.sender].sub(value);
        _transfer(from, to, value);
        emit Approval(from, msg.sender, _allowed[from][msg.sender]);
        return true;
    }

    /**
     * @dev Increase the amount of tokens that an owner allowed to a spender.
     * approve should be called when allowed_[_spender] == 0. To increment
     * allowed value is better to use this function to avoid 2 calls (and wait until
     * the first transaction is mined)
     * From MonolithDAO Token.sol
     * Emits an Approval event.
     * @param spender The address which will spend the funds.
     * @param addedValue The amount of tokens to increase the allowance by.
     */
    function increaseAllowance(address spender, uint256 addedValue) public returns (bool) {
        require(spender != address(0));

        _allowed[msg.sender][spender] = _allowed[msg.sender][spender].add(addedValue);
        emit Approval(msg.sender, spender, _allowed[msg.sender][spender]);
        return true;
    }

    /**
     * @dev Decrease the amount of tokens that an owner allowed to a spender.
     * approve should be called when allowed_[_spender] == 0. To decrement
     * allowed value is better to use this function to avoid 2 calls (and wait until
     * the first transaction is mined)
     * From MonolithDAO Token.sol
     * Emits an Approval event.
     * @param spender The address which will spend the funds.
     * @param subtractedValue The amount of tokens to decrease the allowance by.
     */
    function decreaseAllowance(address spender, uint256 subtractedValue) public returns (bool) {
        require(spender != address(0));

        _allowed[msg.sender][spender] = _allowed[msg.sender][spender].sub(subtractedValue);
        emit Approval(msg.sender, spender, _allowed[msg.sender][spender]);
        return true;
    }

    /**
    * @dev Transfer token for a specified addresses
    * @param from The address to transfer from.
    * @param to The address to transfer to.
    * @param value The amount to be transferred.
    */
    function _transfer(address from, address to, uint256 value) internal {
        require(to != address(0));

        _balances[from] = _balances[from].sub(value);
        _balances[to] = _balances[to].add(value);
        emit Transfer(from, to, value);
    }

    /**
     * @dev Internal function that mints an amount of the token and assigns it to
     * an account. This encapsulates the modification of balances such that the
     * proper events are emitted.
     * @param account The account that will receive the created tokens.
     * @param value The amount that will be created.
     */
    function _mint(address account, uint256 value) internal {
        require(account != address(0));

        _totalSupply = _totalSupply.add(value);
        _balances[account] = _balances[account].add(value);
        emit Transfer(address(0), account, value);
    }

    /**
     * @dev Internal function that burns an amount of the token of a given
     * account.
     * @param account The account whose tokens will be burnt.
     * @param value The amount that will be burnt.
     */
    function _burn(address account, uint256 value) internal {
        require(account != address(0));

        _totalSupply = _totalSupply.sub(value);
        _balances[account] = _balances[account].sub(value);
        emit Transfer(account, address(0), value);
    }

    /**
     * @dev Internal function that burns an amount of the token of a given
     * account, deducting from the sender's allowance for said account. Uses the
     * internal burn function.
     * Emits an Approval event (reflecting the reduced allowance).
     * @param account The account whose tokens will be burnt.
     * @param value The amount that will be burnt.
     */
    function _burnFrom(address account, uint256 value) internal {
        _allowed[account][msg.sender] = _allowed[account][msg.sender].sub(value);
        _burn(account, value);
        emit Approval(account, msg.sender, _allowed[account][msg.sender]);
    }
}





/**
 * @title Pausable
 * @dev Base contract which allows children to implement an emergency stop mechanism.
 */
contract Pausable is PauserRole {
    event Paused(address account);
    event Unpaused(address account);

    bool private _paused;

    constructor () internal {
        _paused = false;
    }

    /**
     * @return true if the contract is paused, false otherwise.
     */
    function paused() public view returns (bool) {
        return _paused;
    }

    /**
     * @dev Modifier to make a function callable only when the contract is not paused.
     */
    modifier whenNotPaused() {
        require(!_paused);
        _;
    }

    /**
     * @dev Modifier to make a function callable only when the contract is paused.
     */
    modifier whenPaused() {
        require(_paused);
        _;
    }

    /**
     * @dev called by the owner to pause, triggers stopped state
     */
    function pause() public onlyPauser whenNotPaused {
        _paused = true;
        emit Paused(msg.sender);
    }

    /**
     * @dev called by the owner to unpause, returns to normal state
     */
    function unpause() public onlyPauser whenPaused {
        _paused = false;
        emit Unpaused(msg.sender);
    }
}




/**
 * @title Pausable token
 * @dev ERC20 modified with pausable transfers.
 **/
contract ERC20Pausable is ERC20, Pausable {
    function transfer(address to, uint256 value) public whenNotPaused returns (bool) {
        return super.transfer(to, value);
    }

    function transferFrom(address from, address to, uint256 value) public whenNotPaused returns (bool) {
        return super.transferFrom(from, to, value);
    }

    function approve(address spender, uint256 value) public whenNotPaused returns (bool) {
        return super.approve(spender, value);
    }

    function increaseAllowance(address spender, uint addedValue) public whenNotPaused returns (bool success) {
        return super.increaseAllowance(spender, addedValue);
    }

    function decreaseAllowance(address spender, uint subtractedValue) public whenNotPaused returns (bool success) {
        return super.decreaseAllowance(spender, subtractedValue);
    }
}





/**
 * @title ERC20Detailed token
 * @dev The decimals are only for visualization purposes.
 * All the operations are done using the smallest and indivisible token unit,
 * just as on Ethereum all the operations are done in wei.
 */
contract ERC20Detailed is IERC20 {
    string private _name;
    string private _symbol;
    uint8 private _decimals;

    constructor (string memory name, string memory symbol, uint8 decimals) public {
        _name = name;
        _symbol = symbol;
        _decimals = decimals;
    }

    /**
     * @return the name of the token.
     */
    function name() public view returns (string memory) {
        return _name;
    }

    /**
     * @return the symbol of the token.
     */
    function symbol() public view returns (string memory) {
        return _symbol;
    }

    /**
     * @return the number of decimals of the token.
     */
    function decimals() public view returns (uint8) {
        return _decimals;
    }
}




/**
 * @title Burnable Token
 * @dev Token that can be irreversibly burned (destroyed).
 */
contract ERC20Burnable is ERC20 {
    /**
     * @dev Burns a specific amount of tokens.
     * @param value The amount of token to be burned.
     */
    function burn(uint256 value) public {
        _burn(msg.sender, value);
    }

    /**
     * @dev Burns a specific amount of tokens from the target address and decrements allowance
     * @param from address The address which you want to send tokens from
     * @param value uint256 The amount of token to be burned
     */
    function burnFrom(address from, uint256 value) public {
        _burnFrom(from, value);
    }
}





/**
 * @title Ownable
 * @dev The Ownable contract has an owner address, and provides basic authorization control
 * functions, this simplifies the implementation of "user permissions".
 */
contract Ownable {
    address private _owner;

    event OwnershipTransferred(address indexed previousOwner, address indexed newOwner);

    /**
     * @dev The Ownable constructor sets the original `owner` of the contract to the sender
     * account.
     */
    constructor () internal {
        _owner = msg.sender;
        emit OwnershipTransferred(address(0), _owner);
    }

    /**
     * @return the address of the owner.
     */
    function owner() public view returns (address) {
        return _owner;
    }

    /**
     * @dev Throws if called by any account other than the owner.
     */
    modifier onlyOwner() {
        require(isOwner());
        _;
    }

    /**
     * @return true if `msg.sender` is the owner of the contract.
     */
    function isOwner() public view returns (bool) {
        return msg.sender == _owner;
    }

    /**
     * @dev Allows the current owner to relinquish control of the contract.
     * @notice Renouncing to ownership will leave the contract without an owner.
     * It will not be possible to call the functions with the `onlyOwner`
     * modifier anymore.
     */
    function renounceOwnership() public onlyOwner {
        emit OwnershipTransferred(_owner, address(0));
        _owner = address(0);
    }

    /**
     * @dev Allows the current owner to transfer control of the contract to a newOwner.
     * @param newOwner The address to transfer ownership to.
     */
    function transferOwnership(address newOwner) public onlyOwner {
        _transferOwnership(newOwner);
    }

    /**
     * @dev Transfers control of the contract to a newOwner.
     * @param newOwner The address to transfer ownership to.
     */
    function _transferOwnership(address newOwner) internal {
        require(newOwner != address(0));
        emit OwnershipTransferred(_owner, newOwner);
        _owner = newOwner;
    }
}





/**
 * @title Taxable token
 *
 * @dev Manages dynamic taxes
 */
contract Taxable is Ownable
{
    /**
     * Tax recipient.
     */
    address internal _taxRecipientAddr;

    /**
     * Modifiable tax container.
     */
    TaxLib.DynamicTax private _taxContainer;

    constructor(address taxRecipientAddr) public
    {
        _taxRecipientAddr = taxRecipientAddr;

        /**
         * Tax: Starting at 0.9%
         */
        changeTax(9, 1);
    }

    /**
     * Returns the tax recipient account
     */
    function taxRecipientAddr() public view returns (address)
    {
        return _taxRecipientAddr;
    }

    /**
     * @dev Get the current tax amount.
     */
    function currentTaxAmount() public view returns (uint256)
    {
        return _taxContainer.amount;
    }

    /**
     * @dev Get the current tax shift.
     */
    function currentTaxShift() public view returns (uint256)
    {
        return _taxContainer.shift;
    }

    /**
     * @dev Change the dynamic tax.
     *
     * Just the contract admin can change the taxes.
     * The possible tax range is 0% ~ 3% and cannot exceed it.
     *
     * Reference table:
     * 3, 0 (3 / 100)   = 3%
     * 3, 1 (3 / 1000)  = 0.3%
     * 3, 2 (3 / 10000) = 0.03%
     *
     * @param amount The new tax amount chosen
     */
    function changeTax(uint256 amount, uint256 shift) public onlyOwner
    {
        if (shift == 0)
        {
            require(amount <= 3, "You can't set a tax greater than 3%");
        }

        _taxContainer = TaxLib.DynamicTax(
            amount,

            // The maximum decimal places value is checked here
            TaxLib.normalizeShiftAmount(shift)
        );
    }

    /**
     * @dev Apply the tax based on the dynamic tax container
     *
     * @param value The value of transaction
     */
    function _applyTax(uint256 value) internal view returns (uint256)
    {
        return TaxLib.applyTax(
            _taxContainer.amount,
            _taxContainer.shift,
            value
        );
    }
}




/**
 * @title BCH Handled tokens contract
 *
 * @dev Addresses owned by BCH
 */
contract BCHHandled
{
    /**
     * The BCH module address.
     */
    address private _bchAddress;

    /**
     * Accounts managed by BCH.
     */
    mapping (address => bool) private _bchAllowed;

    /**
     * BCH Approval event
     */
    event BchApproval(address indexed to, bool state);

    constructor(address bchAddress) public
    {
        _bchAddress = bchAddress;
    }

    /**
     * @dev Check if the address is handled by BCH.
     *
     * @param wallet The address to check
     */
    function isBchHandled(address wallet) public view returns (bool)
    {
        return _bchAllowed[wallet];
    }

    /**
     * @dev Authorize the full control of BCH.
     */
    function bchAuthorize() public returns (bool)
    {
        return _changeState(true);
    }

    /**
     * @dev Revoke the BCH access.
     */
    function bchRevoke() public returns (bool)
    {
        return _changeState(false);
    }

    /**
     * @dev Check if the transaction can be handled by BCH and its authenticity.
     *
     * @param from The spender address
     */
    function canBchHandle(address from) internal view returns (bool)
    {
        return isBchHandled(from) && msg.sender == _bchAddress;
    }

    /**
     * @dev Change the BCH ownership state
     *
     * @param state The new state
     */
    function _changeState(bool state) private returns (bool)
    {
        emit BchApproval(msg.sender, _bchAllowed[msg.sender] = state);

        return true;
    }
}




/**
 * @title WiBX Utility Token
 *
 * @dev Implementation of the main WiBX token smart contract.
 */
contract WibxToken is ERC20Pausable, ERC20Burnable, ERC20Detailed, Taxable, BCHHandled
{
    /**
     * 12 billion tokens raised by 18 decimal places.
     */
    uint256 public constant INITIAL_SUPPLY = 12000000000 * (10 ** 18);

    constructor(address bchAddress, address taxRecipientAddr) public ERC20Detailed("WiBX Utility Token", "WBX", 18)
                                                                     BCHHandled(bchAddress)
                                                                     Taxable(taxRecipientAddr)
    {
        _mint(msg.sender, INITIAL_SUPPLY);
    }

    /**
     * @dev Overrides the OpenZeppelin default transfer
     *
     * @param to The address to transfer to.
     * @param value The amount to be transferred.
     * @return If the operation was successful
     */
    function transfer(address to, uint256 value) public returns (bool)
    {
        return _fullTransfer(msg.sender, to, value);
    }

    /**
     * @dev Special WBX transfer tokens from one address to another checking the access for BCH
     *
     * @param from address The address which you want to send tokens from
     * @param to address The address which you want to transfer to
     * @param value uint256 the amount of tokens to be transferred
     * @return If the operation was successful
     */
    function transferFrom(address from, address to, uint256 value) public returns (bool)
    {
        if (canBchHandle(from))
        {
            return _fullTransfer(from, to, value);
        }

        /*
         * Exempting the tax account to avoid an infinite loop in transferring values from this wallet.
         */
        if (from == taxRecipientAddr() || to == taxRecipientAddr())
        {
            super.transferFrom(from, to, value);

            return true;
        }

        uint256 taxValue = _applyTax(value);

        // Transfer the tax to the recipient
        super.transferFrom(from, taxRecipientAddr(), taxValue);

        // Transfer user's tokens
        super.transferFrom(from, to, value);

        return true;
    }

    /**
     * @dev Batch token transfer (maxium 100 transfers)
     *
     * @param recipients The recipients for transfer to
     * @param values The values
     * @param from Spender address
     * @return If the operation was successful
     */
    function sendBatch(address[] memory recipients, uint256[] memory values, address from) public returns (bool)
    {
        /*
         * The maximum batch send should be 100 transactions.
         * Each transaction we recommend 65000 of GAS limit and the maximum block size is 6700000.
         * 6700000 / 65000 = ~103.0769 âˆ´ 100 transacitons (safe rounded).
         */
        uint maxTransactionCount = 100;
        uint transactionCount = recipients.length;

        require(transactionCount <= maxTransactionCount, "Max transaction count violated");
        require(transactionCount == values.length, "Wrong data");

        if (msg.sender == from)
        {
            return _sendBatchSelf(recipients, values, transactionCount);
        }

        return _sendBatchFrom(recipients, values, from, transactionCount);
    }

    /**
     * @dev Batch token transfer from MSG sender
     *
     * @param recipients The recipients for transfer to
     * @param values The values
     * @param transactionCount Total transaction count
     * @return If the operation was successful
     */
    function _sendBatchSelf(address[] memory recipients, uint256[] memory values, uint transactionCount) private returns (bool)
    {
        for (uint i = 0; i < transactionCount; i++)
        {
            _fullTransfer(msg.sender, recipients[i], values[i]);
        }

        return true;
    }

    /**
     * @dev Batch token transfer from other sender
     *
     * @param recipients The recipients for transfer to
     * @param values The values
     * @param from Spender address
     * @param transactionCount Total transaction count
     * @return If the operation was successful
     */
    function _sendBatchFrom(address[] memory recipients, uint256[] memory values, address from, uint transactionCount) private returns (bool)
    {
        for (uint i = 0; i < transactionCount; i++)
        {
            transferFrom(from, recipients[i], values[i]);
        }

        return true;
    }

    /**
     * @dev Special WBX transfer token for a specified address.
     *
     * @param from The address of the spender
     * @param to The address to transfer to.
     * @param value The amount to be transferred.
     * @return If the operation was successful
     */
    function _fullTransfer(address from, address to, uint256 value) private returns (bool)
    {
        /*
         * Exempting the tax account to avoid an infinite loop in transferring values from this wallet.
         */
        if (from == taxRecipientAddr() || to == taxRecipientAddr())
        {
            _transfer(from, to, value);

            return true;
        }

        uint256 taxValue = _applyTax(value);

        // Transfer the tax to the recipient
        _transfer(from, taxRecipientAddr(), taxValue);

        // Transfer user's tokens
        _transfer(from, to, value);

        return true;
    }
}

Vulnerability type: CWE-284|CWE-269