No storage gap for upgradeable contracts

[code423n4]

Lines of code

https://github.com/code-423n4/2022-10-blur/blob/2fdaa6e13b544c8c11d1c022a575f16c3a72e3bf/contracts/BlurExchange.sol#L30

Vulnerability details

Impact

BlurExchange.sol

BlurExchange is an upgradeable contract inheriting some other contract. In case the contract need to be upgraded and inheriting new contract that use storage, the current storage slot may be collising . To prevent overriden storage slot, the contract should added a storage gap.

if storage gap ain't added, the contract may not introduce new variable at the inheriting contract.

Proof of Concept

BlurExchange

    /// current inheritance 
    contract BlurExchange is IBlurExchange, ReentrancyGuarded, EIP712, OwnableUpgradeable, UUPSUpgradeable {
        ...
    }

    /// In case the contract need more inheritance 
    contract BlurExchange is MaybeSomethingContract, IBlurExchange, ReentrancyGuarded, EIP712, OwnableUpgradeable, UUPSUpgradeable {
        ...
    }

Tools Used

VSCode

Recommended Mitigation Steps

Consider adding a storage gap at the start of the upgradeable contract

[GalloDaSballo]

Dup of #410

[GalloDaSballo]

L