XSS is a security flaw in web applications where attackers inject malicious scripts into web pages that other users view and interact with.
We have some different kind of XSS which are used for different purposes in different time
Happens when malicious script is permanently stored on target servers, such as in comment sections and form user can put malicious script in your database if you do not have a proper validation for your input fields
Occur when malicious script is embedded in a URL, which execute when a URL is visited
Involves client-side code vulnerability where the document object model (DOM) environment is manipulated.
to prevent from XSS attack developer must follow procedure called sanitizing input field
User input (Can put Scripts by form inputs and URL)
Malicious Content (Posting string in users generated areas like comments where everybody comments)
Third Party Components (When you are using third party plugins, and they contain vulnerabilities, and attacker can use malicious script in plugin to exploit site)
Companies might face significant financial losses due to stolen data or fraud
A Successful XSS attack can damage company reputation and lost of user trust
Business may face legal actions if customer data is compromised
Tools For XSS Identification (like automatic security tool like owasp,berksuit and XSS Scanners)
Manual testing
Check eye on frequent unusual popups and redirects
Use HTTP security headers (X content,X Acess)