Mystery Box

Summary:

The openBox() function uses pseudo-randomness by relying on block.timestamp and msg.sender, which are easily predictable. This vulnerability allows attackers to manipulate reward outcomes and consistently win high-value rewards.

Vulnerability Details:

The random value in the openBox() function is calculated using block.timestamp and msg.sender, which are publicly accessible values that can be predicted or manipulated by miners or attackers.

• Location: openBox()

  uint256 randomValue = uint256(keccak256(abi.encodePacked(block.timestamp, msg.sender))) % 100;

Impact:

• Predictable Rewards: Attackers can manipulate block timestamps or craft transactions to increase the likelihood of receiving more valuable rewards, thereby undermining the integrity of the reward system.

• Economic Loss: Legitimate users may receive only low-value rewards, while attackers consistently gain higher-value rewards, leading to significant financial imbalances.

Tools Used:

• Manual Code Review

• Remix IDE

Recommendations

Recommendations:
Use an external oracle service, such as Chainlink VRF, for secure and verifiable randomness generation.