Blockchain Smart Contract Vulnerabilities

Question 1

What is a common vulnerability that allows repeated withdrawals in smart contracts?

Accepted Answer

Reentrancy

Answer

Reentrancy attacks occur when a function makes an external call to another untrusted contract before it resolves its own logic.

Question 2

Why is input validation critical in smart contracts?

Accepted Answer

To ensure logical correctness and safety

Answer

Without input validation, contracts can be tricked into performing unintended actions or altering expected outcomes.

Question 3

Which vulnerability can allow funds to be locked indefinitely in a contract?

Accepted Answer

Fallback function flaw

Answer

A contract with a missing or broken fallback mechanism may prevent fund retrieval, leading to permanent fund loss.

Question 4

What is the purpose of using the 'checks-effects-interactions' pattern?

Accepted Answer

To defend against reentrancy attacks

Answer

This pattern reduces the risk of reentrancy by ensuring that all internal logic updates occur before calling external contracts.

Question 5

Which tool is commonly used to audit smart contracts for vulnerabilities?

Accepted Answer

MythX

Answer

MythX is a widely used security analysis tool for detecting smart contract vulnerabilities through automated testing.

Blockchain Practice Test