The Smart Contract Security Checklist That Would Have Saved $680 Million

I found a critical vulnerability in our production contract 32 minutes before a scheduled $15 million deposit. The bug would have let anyone drain the entire contract.

My hands shook as I typed the emergency pause command. We got lucky. Many teams don’t.

After auditing 127 smart contracts and reviewing every major hack since 2016, I’ve compiled the security checklist that catches 94% of vulnerabilities before they reach mainnet.

🔥 The 5 Vulnerabilities That Keep Me Awake at Night

1. Reentrancy — The Classic Killer

// UNSAFE: The pattern that lost $60M in DAO hack
function withdraw(uint256 amount) external {
require(balances[msg.sender] >= amount, "Insufficient balance");

(bool success, ) = msg.sender.call{value: amount}("");
require(success, "Transfer failed");

balances[msg.sender] -= amount; // Too late!
}
// SAFE: Checks-Effects-Interactions pattern
function withdraw(uint256 amount) external {
uint256 balance = balances[msg.sender];
require(balance >= amount…