Blockchain Developer FREE Blockchain Developer Blockchain Security and Vulnerabilities Questions and Answers 2

Question 1

What is a flash loan attack in DeFi?

Accepted Answer

Exploiting uncollateralized loans within a single transaction to manipulate protocol state

Answer

Flash loan attacks exploit the ability to borrow large amounts without collateral within one transaction, using the funds to manipulate prices or exploit vulnerable smart contracts before repaying.

Question 2

Which vulnerability does the Checks-Effects-Interactions pattern specifically prevent?

Accepted Answer

Reentrancy attacks

Answer

The Checks-Effects-Interactions pattern prevents reentrancy by updating contract state before making external calls, so re-entrant calls see the already-updated state.

Question 3

What is transaction front-running on a blockchain?

Accepted Answer

Submitting a transaction with higher gas to execute before a pending target transaction

Answer

Front-running involves observing a pending transaction in the mempool and submitting a competing transaction with higher gas fees to get it mined first.

Question 4

What is the primary risk of using tx.origin for authentication in Solidity?

Accepted Answer

A malicious intermediate contract can pass the tx.origin check of the original sender

Answer

Using tx.origin for auth is dangerous because if a user interacts with a malicious contract, that contract can call the target contract and tx.origin will still be the user's address.

Question 5

Which attack vector targets the random number generation in smart contracts that use block variables?

Accepted Answer

Block timestamp manipulation by miners

Answer

Miners can influence block timestamps and other block variables within certain bounds, making on-chain randomness based on these values predictable and exploitable.

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Blockchain Developer FREE Blockchain Developer Blockchain Security and Vulnerabilities Questions and Answers 2