QA Report

[code423n4]

1. safeApprove() is deprecated

Description

Deprecated in favor of safeIncreaseAllowance() and safeDecreaseAllowance().Whenever possible, use {safeIncreaseAllowance} and {safeDecreaseAllowance} instead. This is probably an oversight since SafeERC20 was imported and safeTransfer() was used for ERC20 token transfers. Nevertheless, note that approve() will fail for certain token implementations that do not return a boolean value (). Hence it is recommend to use safeApprove().

Proof of concept

Bug

src/frxETHMinter.sol:75:        frxETHToken.approve(address(sfrxETHToken), msg.value);

Recommendation

Update to frxETHToken.safeApprove(spender, msg.value) in the function.

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2. Avoid using Floating Pragma:

Description

Contracts should be deployed with the same compiler version and flags that they have been tested with thoroughly. Locking the pragma helps to ensure that contracts do not accidentally get deployed using, for example, an outdated compiler version that might introduce bugs that affect the contract system negatively. The pragma declared across the solution is ^0.8.0 As the compiler introduces a several interesting upgrades in newer versions of Solidity consider locking at this version or a more recent one.

Bug

lib/ERC4626/src/xERC4626.sol:4:pragma solidity ^0.8.0;
src/frxETHMinter.sol:2:pragma solidity ^0.8.0;
src/ERC20/ERC20PermitPermissionedMint.sol:2:pragma solidity ^0.8.0;
src/sfrxETH.sol:2:pragma solidity ^0.8.0;
src/frxETH.sol:2:pragma solidity ^0.8.0;
src/OperatorRegistry.sol:2:pragma solidity ^0.8.0;

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3. _safeMint() should be used rather than _mint() wherever possible

Description

_mint() is discouraged in favor of _safeMint() which ensures that the recipient is either an EOA or implements IERC721Receiver.

Bugs

src/ERC20/ERC20PermitPermissionedMint.sol:60:        super._mint(m_address, m_amount);

Recommendations:

Use _safeMint() instead of _mint().

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4. Event is missing indexed fields

Description

Each event should use three indexed fields if there are three or more fields

Bugs

src/OperatorRegistry.sol:212:    event ValidatorRemoved(bytes pubKey, uint256 remove_idx, bool dont_care_about_ordering);
src/OperatorRegistry.sol:214:    event ValidatorsSwapped(bytes from_pubKey, bytes to_pubKey, uint256 from_idx, uint256 to_idx);