Ethernaut by OpenZeppelin is a great learning resource for EVM learner for some crucial knowledge - storage layout, delegatecall, selfdestruct, and more. Learn about the functionalities and more importantly, the pitfalls for potential risk on security. Sharing my experience and the tips for cracking the levels.

Useful Links (Tools)

• Ethernaut: https://ethernaut.openzeppelin.com/
• Remix: https://remix.ethereum.org/
• Abi encoding: https://abi.hashex.org/
• Block Explorer: https://goerli.etherscan.io/
• Hex-Dec converter: https://www.rapidtables.com/convert/number/hex-to-decimal.html

Levels

Hello Ethernaut

• This exercise is trivial. Just follow the info(), get the password and call authenticate()

Fallback

• Call contribute() with a tiny amount
• Send a tiny amount to the contract and the owner will be changed (trigger receive())
• Call withdraw() to get all the amount
• Fallout
  • There’s a typo on method Fal1out() . Just call it and you can get the owner

CoinFlip

• The contract use the block value to determine the flipping result
• Create another contract to trigger the guess. Within the same transaction we can get the exact same block value as the checking method, so we can always pre-compute the correct answer
• contract code snippet