What Is Cross Site Scripting Medium?


Scott Campbell

What Is Cross Site Scripting Medium?

Cross Site Scripting (XSS) is a type of security vulnerability commonly found in web applications. It occurs when an attacker injects malicious scripts into a trusted website, which then executes those scripts on the user’s browser. XSS can be devastating as it allows attackers to steal sensitive information, hijack user sessions, or even deface websites.

Types of XSS Attacks:

There are three main types of XSS attacks:

1. Reflected XSS:
– Reflected XSS occurs when user input is immediately returned by the web application without proper sanitization.

– Attackers craft malicious URLs and trick users into clicking on them. – The injected script executes in the victim’s browser, leading to potential data theft or unauthorized actions.

2. Stored XSS:
– Stored XSS is more dangerous as the injected script is permanently stored on the Target server.

– Attackers can inject malicious code into forums, comment sections, or any input fields that allow HTML content. – Whenever other users access the affected page, the script executes automatically.

3. DOM-based XSS:
– DOM-based XSS occurs when client-side JavaScript reads data from an untrusted source and injects it into the Document Object Model (DOM).
– The injected script manipulates the DOM and can lead to various security issues.

Preventing Cross Site Scripting Attacks:

Protecting against cross-site scripting attacks requires a multi-layered approach:

1. Input Validation and Sanitization:
– Validate and sanitize user input before accepting it in your application.
– Use secure coding practices and frameworks that provide built-in protections against XSS vulnerabilities.

2. Output Encoding:
– Encode all output properly to prevent browsers from interpreting it as executable code.
– HTML entities should be encoded to their corresponding character codes.

3. Content Security Policy (CSP):
– Implement a Content Security Policy to restrict which scripts can be executed on your website.
– Whitelist trusted sources and block any unauthorized scripts.

4. HTTP-only Cookies:
– Set the “HttpOnly” flag on cookies to prevent client-side scripts from accessing them.
– This helps mitigate session hijacking attacks.

5. Regular Security Audits:
– Regularly audit your codebase for potential XSS vulnerabilities.
– Keep up with security best practices and stay informed about the latest attack vectors.


Cross Site Scripting (XSS) is a severe security vulnerability that can expose users to various risks. Understanding the different types of XSS attacks and implementing proper prevention techniques is crucial for web developers.

By validating user input, encoding output, and implementing additional security measures, you can significantly reduce the risk of XSS vulnerabilities in your applications. Stay vigilant and stay secure!

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