The browser is doing more security work than you realize. Here's what happens when you accidentally get in its way. In this article we'll cover how XSS actually happens in real frontend codebases, how CSRF works and where the browser's default protections break down, how clickjacking works and how one header stops it, what Content Security Policy actually does and how to implement it without breaking your app, and the CORS misconfigurations that create vulnerabilities while feeling like security. Frontend security has a reputation for being someone else's problem. The backend handles auth, the infrastructure team handles firewalls and the frontend just renders what it's given. That mindset is expensive. I've worked on platforms handling more than 10 million active users. At that scale, a single security misconfiguration isn't a bug report - it's an incident. And the uncomfortable truth is that most of the vulnerabilities I've seen on the frontend weren't sophisticated attacks.…