The Standard

Summary

In the context of upgradeable contracts, ensuring forward compatibility between different contract versions is a critical concern. One key strategy for ensuring this compatibility is the use of a __gap storage variable.

Vulnerability Details

The __gap variable acts as a reserved space in the contract's storage layout. This space can then be utilized for adding new state variables in future contract upgrades, while maintaining the original storage layout of the contract.

Without the __gap storage variable, adding new state variables in a contract upgrade can risk overwriting the existing contract storage, potentially leading to unpredictable behavior or data loss.

Therefore, if your contract is designed to be upgradeable, it's crucial to include a __gap storage variable. The absence of this variable in an upgradeable contract can signify a potential risk for future upgrades.

Tools Used

VSCode

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add __gap[50] storage variable