Understanding Web3 Vulnerabilities

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🔓 Understanding Web3 Vulnerabilities - A Deep Dive for Ethical Hackers​

Web3 introduces a decentralized future, but with new power comes new attack surfaces. Let’s break down the most critical Web3 vulnerabilities, their real-world examples, and the tools used to detect/exploit them.

🧨 1. Re-Entrancy Attack​

A classic vulnerability in Ethereum smart contracts.
🧪 Example:
The infamous DAO Hack (2016) resulted in the theft of ~3.6 million ETH.
🛠️ Code Snippet:
PHP:
function withdraw(uint _amount) public {
    if (balances[msg.sender] >= _amount) {
        (bool success, ) = msg.sender.call{value: _amount}("");
        require(success);
        balances[msg.sender] -= _amount;
    }
}
👨‍💻 Attacker creates a fallback function to recursively call withdraw() before balance is updated.

🧰 Tool to test:
Mythril
Slither
Echidna (fuzzing)

🔐 2. Integer Overflow/Underflow​

Before Solidity 0.8, arithmetic was unchecked.
🧪 Example:
Code:
uint8 x = 255;
x += 1; // x becomes 0 (overflow)
✅ Fixed in latest Solidity, but legacy contracts still vulnerable.
🧰 Tools:
Slither
Manticore

🪤 3. Phishing via Web3 Wallets (Front-end Attacks)​

Users tricked into signing malicious transactions via fake UI/popups.
🧪 Example:
Fake airdrop site asks user to “claim” tokens but actually steals all NFTs.
🔧 Tools to simulate/analyze:
Browser dev tools
Metamask + testnet

📬 4. Unprotected selfdestruct() Calls​

Smart contracts can be killed if access control is misconfigured.
🧪 Example:
PHP:
function kill() public {
    selfdestruct(payable(msg.sender));
}
👨‍💻 If no onlyOwner modifier is used, any user can destroy the contract.
🧰 Tool:
Slither
Mythril

🕳️ 5. Oracle Manipulation Attacks​

Manipulate price feeds to exploit DeFi protocols.
🧪 Example:
Flashloan used to temporarily inflate token price, borrow more than collateral worth.
🧰 Tools:
Tenderly (debug transactions)
Foundry/Hardhat for simulations

🧪 Bonus: Common Testing Tools for Web3 Pentesters​

Tool Use Case
Slither Static analysis of contracts
Mythril Vulnerability scanning
Echidna Fuzzing smart contracts
Tenderly Real-time monitoring/debugging
Foundry Contract development + testing
Remix IDE Manual testing/debugging

🚨 Final Words
Web3 is powerful but not bulletproof. Every smart contract is a potential target. Always audit your contracts and test thoroughly before mainnet deployment.
 
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