Third-party scripts execute with the same level of trust as your own code once they load in the browser. Your server delivers the page, but you do not control what a third-party vendor delivers afterward. If a vendor's CDN is compromised, every site loading that script inherits the attacker's code, which is how Magecart campaigns compromise thousands of merchants at once. Scripts can also update silently, read any form field on the page, and activate only under specific conditions that crawlers never observe.
How do client-side attacks actually happen?
Compromising a third-party service your website relies on is one common way attackers get in.
Why can't traditional security tools detect client-side threats?
Firewalls, WAFs, and vulnerability scanners are traditional security tools used to protect your server, but they cannot see what's happening in your users' browsers.
What's the difference between client-side security and server-side security?
Server-side security protects your infrastructure, while client-side security focuses on where your application actually runs, inside your users' browsers.
What's the difference between client-side security and application security?
Client-side security is a critical subset of AppSec that focuses on protecting applications where they actually execute--in users' browsers.