XSS (Cross-Site Scripting) is a security vulnerability typically found in web applications that allows attackers to inject malicious scripts into content from otherwise trusted websites. These scripts can then be executed by unsuspecting users, potentially leading to various attacks.

Types of XSS Attacks

• Stored XSS: Malicious script is permanently stored on the target server, such as in a database or forum post, and is served to users whenever they request the affected content.
• Reflected XSS: Malicious script is embedded in a URL and reflected back to the user by the web server. When the user clicks the link, the script executes in their browser.
• DOM-Based XSS: Malicious script is executed as a result of modifying the Document Object Model (DOM) of the webpage in the user's browser.

Consequences of XSS Attacks

• Session Hijacking: Attackers can steal session cookies, allowing them to impersonate the user.
• Defacement: Attackers can alter the content of a website, displaying unwanted or harmful content.
• Data Theft: Malicious scripts can steal sensitive information, such as login credentials and personal data.
• Malware Distribution: XSS can be used to distribute malware by injecting malicious code into trusted websites.
• Phishing: Attackers can use XSS to create fake login forms and steal user credentials.

Preventing XSS Attacks

• Input Validation: Validate and sanitize all user inputs to ensure they do not contain malicious scripts.
• Output Encoding: Encode output data to prevent it from being interpreted as executable code by the browser.
• Use Security Libraries: Implement security libraries and frameworks that provide built-in protection against XSS.
• Content Security Policy (CSP): Use CSP headers to restrict the sources from which content can be loaded and executed.
• Regular Security Testing: Conduct regular security testing, including code reviews and penetration testing, to identify and address XSS vulnerabilities.