Root + Impact

The pseudo-random seed uses keccak256(concat(convert(block.timestamp, bytes32), convert(msg.sender, bytes32))). This is predictable and manipulable by miners (they influence timestamp slightly) and by users (msg.sender is known).

Description

• Attackers (or miners) can bias requested or extra_item_chance to obtain more items, especially when inventory is low. This can be used to drain inventory or exploit timing.

Risk

Likelihood:

• A miner can include a transaction at a timestamp that yields a favorable seed or an attacker can try call ordering/back-running to hit a favorable block timestamp.

Proof of Concept

Recommended Mitigation

• Use a secure randomness source (Chainlink VRF) for important value. If VRF is not available, do not rely on on-chain timestamp randomness for value-sensitive decisions; at minimum use blockhash of a previous block (still not secure) and combine multiple entropy sources and limit the impact of randomness on economic outcome.