[L-01] address(0) check missing in functions

https://github.com/Cyfrin/2023-07-beedle/blob/main/src/utils/Ownable.sol#L14-L17

https://github.com/Cyfrin/2023-07-beedle/blob/main/src/Lender.sol#L100-L102

https://github.com/Cyfrin/2023-07-beedle/blob/main/src/Staking.sol#L31-L34

Recommendation

Add a check if != address(0)

[L-02] safeTransfer and safeTransferFrom methods should be used for token transfers

https://github.com/Cyfrin/2023-07-beedle/blob/main/src/Staking.sol#L39

https://github.com/Cyfrin/2023-07-beedle/blob/main/src/Staking.sol#L49

https://github.com/Cyfrin/2023-07-beedle/blob/main/src/Staking.sol#L55

https://github.com/Cyfrin/2023-07-beedle/blob/main/src/Fees.sol#L43

https://github.com/Cyfrin/2023-07-beedle/blob/main/src/Lender.sol#L152

https://github.com/Cyfrin/2023-07-beedle/blob/main/src/Lender.sol#L159

https://github.com/Cyfrin/2023-07-beedle/blob/main/src/Lender.sol#L187

https://github.com/Cyfrin/2023-07-beedle/blob/main/src/Lender.sol#L203

https://github.com/Cyfrin/2023-07-beedle/blob/main/src/Lender.sol#L267-L271

https://github.com/Cyfrin/2023-07-beedle/blob/main/src/Lender.sol#L317-L329

https://github.com/Cyfrin/2023-07-beedle/blob/main/src/Lender.sol#L403

https://github.com/Cyfrin/2023-07-beedle/blob/main/src/Lender.sol#L505

https://github.com/Cyfrin/2023-07-beedle/blob/main/src/Lender.sol#L563-L565

https://github.com/Cyfrin/2023-07-beedle/blob/main/src/Lender.sol#L642-L670

Recommendation

User safeTransfer and safeTransferFrom instead of safeERC20 library

https://github.com/OpenZeppelin/openzeppelin-contracts/blob/master/contracts/token/ERC20/utils/SafeERC20.sol

[L-03] Validation checks missing

Add a check of amount != 0 and _profits != address(0)
https://github.com/Cyfrin/2023-07-beedle/blob/main/src/Fees.sol#L28

Add a check of _amount != 0
https://github.com/Cyfrin/2023-07-beedle/blob/main/src/Staking.sol#L38

Add a check that _amount != 0 and _amount <= balances[msg.sender]
https://github.com/Cyfrin/2023-07-beedle/blob/main/src/Staking.sol#L46

Add a check that _weth != address(0) and _staking != address(0)
https://github.com/Cyfrin/2023-07-beedle/blob/main/src/Fees.sol#L19-L22

Add a check that claimable[msg.sender] <= WETH.balanceOf(address(this)
https://github.com/Cyfrin/2023-07-beedle/blob/main/src/Staking.sol#L55

Add a check that amount <= pools[poolId].poolBalance in the begining
https://github.com/Cyfrin/2023-07-beedle/blob/main/src/Lender.sol#L198

[L-04] Length of arrays validation missing

The length of arrays should be matched before the iteration to avoid unexpected behaviour

https://github.com/Cyfrin/2023-07-beedle/blob/main/src/Lender.sol#L359

Recommendation

The size of loanIds and poolIds should be equal before iterating over them.