What's the fundamental difference between server-side attacks that WAFs catch and client-side attacks miss?

Server-side attacks target your web server infrastructure through malicious requests, SQL injections, or application vulnerabilities. This is where WAFs excel. Client-side attacks exploit legitimate third-party scripts that your WAF has already approved and delivered to browsers. The attack happens when these scripts execute in your users' browsers and steal data like credit card numbers or login credentials. Your WAF sees the legitimate script delivery, but is blind to what that script does once it's running on the client-side.