What are Cross-Site Scripting (XSS) attacks ?

Hi,

I think OWASP has the best answers to this:

https://www.owasp.org/index.php/Cross-site_Scripting_(XSS)

Preventing this takes steps on front and back. Plus, it depends on the programing language you are using and the framework.

XSS is a security breach that takes advantage of dynamically generated Web pages.

it enables attackers to inject client-side scripts into web pages viewed by other users

Thank you for the question, I learnt from previous answers

The idea of xss is that a hacker can inject their own custom JavaScript into a webpage. It's used to trick users into running their custom JavaScript code. And they also used to steal cookies. And if they steal cookies they can steal the cookies data as well as potentially session data, which has been linked with a cookie.

XSS(cross site scripting) in simple words is running user written script in text input box of any website and watching the same script reflecting on the website, which is a huge vulnerability, without any admin privilege a Attacker will be able to manipulate or change website's UI with which one can be fooled for malicious content or attacker might steal cookies with session information etc, brief explanation on this can be obtained at OWASP or Acunetix website.

really its a big gap in web site design ...why its famous Gap

 because meny of  web sites like Apple ,Uponto its hacked by this gap

this depend on Client Side programming Languages 

see that to understand more

https://www.acunetix.com/websitesecurity/cross-site-scripting/

Basm allah alrahman alrahim

look at wikipedia XSS