Missing storage gaps in upgradeable contract

The upgradeable contracts lack storage gap variables (__gap). Storage gaps reserve storage slots for future versions, preventing storage collisions when new state variables are added during upgrades of parent contracts.

Future upgrades that add state variables to parent contracts could overwrite or shift the layout of derived contract variables, leading to corrupted storage and incorrect behaviour.

Add a storage gap at the end of the contract to reserve slots for future upgrades:

// Reserved storage space to allow for layout changes in the future.
uint256[50] private __gap;

This should be placed just before the closing brace of the contract. The size of the gap (50 in this example) can be adjusted based on anticipated future needs, but 50 is a common value used in OpenZeppelin's upgradeable contracts.

Ipal Network: Confirmed. We agreed with the recommendation.

Zealynx: Not Fixed: Neither contract implements storage gaps. The main KnowledgeMarket.sol contract lacks the recommended uint256[50] private __gap; variable to reserve storage slots for future upgrades.

UPDATE: Fixed.