First Flight #10: One Shot

Summary

The mintRapper function in OneShot.sol improperly initialises OneShot::rapperStats before any gameplay, granting newly minted NFTs unearned skill advantages, which undermines the intended game mechanics.

Vulnerability Details

The default values of OneShot::rapperStats for a newly minted NFT are beneficial to the player (weakKnees: false, heavyArms: false, spaghettiSweater: false, calmAndReady: false, battlesWon: 0). Score +15 already.

A malicious player could take control when he receives a NFT with a custom implementation of onERC721Received. He will then reenter on RapBattle::goOnStageOrBattle.

Impact

It gives an unfair advantage to players who mint new NFTs. Nevertheless the game is also based on chance in the end.

Tools Used

Manual Review

Recommendations

Restructure the OneShot::mintRapper to follow the Checks-Effects-Interactions pattern strictly. Ensure all state changes are performed before any extenal interaction.