Cross-Site Scripting (XSS) Attack

Cross-Site Scripting (XSS) Attack: An Overview

Introduction

Cross-Site Scripting (XSS) is a security vulnerability that allows attackers to inject malicious scripts into web pages viewed by users. This type of attack can be used to steal sensitive data, manipulate website content, or redirect users to malicious sites.

Types of XSS Attacks

There are three main types of XSS attacks:

1. Stored XSS: Malicious script is permanently injected into a website's database and displayed to users whenever they visit the affected page.

2. Reflected XSS: The attack script is embedded in a URL or input field and executed when a user clicks a malicious link or submits a form.

3. DOM-Based XSS: The attack occurs when JavaScript in the browser modifies the Document Object Model (DOM), executing harmful scripts.

How XSS Works

• The attacker injects malicious JavaScript into a website’s input fields or URLs.

• The injected script is processed by the browser and executed unknowingly by the victim.

• The malicious code can steal cookies, session tokens, or other sensitive user data, allowing attackers to impersonate users.

Real-World Examples

Some ways attackers use XSS include:

• Session Hijacking: Stealing login credentials or session tokens.

• Defacing Websites: Altering site content to display unwanted messages or offensive material.

• Phishing Attacks: Redirecting users to fake login pages to steal their credentials.

Prevention Techniques

Web developers can protect applications from XSS using several security measures:

1. Input Validation & Sanitization: Ensure user input is properly filtered to remove harmful characters.

2. Content Security Policy (CSP): Restrict the execution of unauthorized scripts.

3. Escaping Output: Encode data before displaying it to prevent unintended execution.

4. Use Secure HTTP Headers: Implement headers like X-XSS-Protection to strengthen security.

Conclusion

Cross-Site Scripting is a dangerous vulnerability that can compromise user data, manipulate web applications, and enable phishing attacks. Developers must adopt best practices to safeguard applications from XSS threats.