The XSS Patterns Hackers Use (And How to Spot Them)

XSS — Cross-Site Scripting — has been the #1 web vulnerability in bug bounty programs for years running. Not because it's exotic or clever, but because developers keep making the same five mistakes. Learn to recognize those mistakes, and you can both harden your own apps and earn real money finding them in other people's. This article covers the five XSS patterns that actually show up in bug bounties, how to test for each one in under 30 seconds, and how to write a report that gets paid. Why XSS Is Still Everywhere in 2026 You'd think sanitizing user input would be table stakes by now. It is — in theory. In practice: Teams move fast and add new input fields without security review Third-party components introduce vectors the original team didn't write SPAs shifted rendering client-side, where developers think server rules still protect them Developers sanitize for one context (HTML) and forget another (JavaScript, URLs, attributes) The result: XSS findings are still being paid out week