The OWASP Top 10 (2025): 10 Ways Developers Are Handing Attackers the Keys Every major breach you've read about in the last five years? It was probably on this list. The OWASP Top 10 is updated every few years. It is not theory. It is a leaderboard of the most exploited vulnerabilities in production systems, right now, in companies with real engineering teams and real security budgets. Here are all 10. With receipts. #1 — Broken Access Control Still number one. Has been number one since 2021. This is what happens when your server trusts the client to tell it what data to fetch — and never checks whether that user actually owns it. The attack is almost embarrassingly simple. You change a number in a URL or a request body. user_id=1001 becomes user_id=1002 . Server returns someone else's data. No hacking. Just counting. Real world: In 2022, Optus — Australia's second-largest telco — exposed nearly 10 million customer records through an unauthenticated API endpoint. No authentication required.…