Mystery Box

Summary

The claimSingleReward function is also vulnerable to a reentrancy attack, similar to the claimAllRewards function.

Vulnerability Details

The claimSingleReward function sends Ether to the caller before updating the state, allowing for potential reentrancy:

Impact

High. An attacker could repeatedly claim the same reward, draining more Ether than they should receive.

Tools Used

Manual code review

Recommendations

Implement the checks-effects-interactions pattern:

• First, store the value and delete the reward

• Then, transfer the Ether

Consider using OpenZeppelin's ReentrancyGuard contract to add a nonReentrant modifier to sensitive functions.