Cross Site Scripting
In plain terms
Injecting malicious scripts into pages other users view.
Going deeper
XSS occurs when an app renders untrusted input as executable script in users' browsers, enabling session theft or page manipulation. It exploits trust in a site.
Under the hood
Stored, reflected, and DOM-based variants; prevented via output encoding and Content Security Policy.
Examples
Injected <script>, cookie theft, defacement, CSP defense, input sanitization.
Think of it like...
Like sneaking a hypnotic note onto a public board that controls whoever reads it.