Penetration Testing a Vulnerable Bank App: Key Techniques and Lessons

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Introduction

Application penetration testing is a critical skill for cybersecurity professionals, helping identify vulnerabilities before malicious actors exploit them. In this article, we explore a real-world penetration testing exercise on a Vulnerable Bank App, uncovering security flaws and demonstrating remediation techniques.

Learning Objectives

  • Understand common vulnerabilities in banking applications.
  • Learn practical exploitation techniques for web app security testing.
  • Apply secure coding and hardening measures to mitigate risks.

1. SQL Injection Exploitation

Command:

' OR 1=1 --

Step-by-Step Guide:

  1. Identify Input Fields: Test login forms, search bars, or URL parameters.
  2. Inject Payload: Enter the SQL command to bypass authentication.
  3. Analyze Response: If the application logs you in without credentials, SQLi is confirmed.
  4. Mitigation: Use parameterized queries or ORMs like SQLAlchemy.

2. Cross-Site Scripting (XSS) Attack

Command:

<script>alert('XSS')</script>

Step-by-Step Guide:

  1. Test Input Fields: Insert the script into comment sections or user profiles.
  2. Check Execution: If an alert pops up, the app is vulnerable.

3. Mitigation: Sanitize inputs using libraries like DOMPurify.

3. Broken Authentication Bypass

Command (Using Burp Suite):

POST /login HTTP/1.1 
Host: vulnerablebank.com 
Content-Type: application/json 
{"username":"admin", "password":"' OR '1'='1"}

Step-by-Step Guide:

  1. Intercept Login Request: Use Burp Suite to capture the login attempt.
  2. Modify Payload: Inject SQL or manipulate session tokens.

3. Mitigation: Implement multi-factor authentication (MFA).

4. Insecure Direct Object Reference (IDOR)

Command (URL Manipulation):

https://vulnerablebank.com/user?id=123 → https://vulnerablebank.com/user?id=124

Step-by-Step Guide:

  1. Change Parameter Values: Alter IDs in URLs to access unauthorized data.

2. Verify Access: If data loads, IDOR exists.

3. Mitigation: Implement proper access controls.

5. Security Misconfigurations

Command (Nmap Scan):

nmap -sV --script vuln vulnerablebank.com

Step-by-Step Guide:

  1. Scan for Open Ports: Identify unnecessary services (e.g., FTP, Telnet).
  2. Check Default Credentials: Test admin:admin on exposed panels.
  3. Mitigation: Disable unused services and enforce strong passwords.

6. API Security Testing

Command (JWT Token Tampering):

jwt_tool <JWT_TOKEN> -T

Step-by-Step Guide:

  1. Capture API Requests: Use Burp Suite or Postman.
  2. Decode & Modify Tokens: Alter claims (e.g., `”role”:”user”` → "role":"admin").

3. Mitigation: Use short-lived tokens and validate signatures.

7. Cloud Hardening (AWS S3 Bucket Misconfigurations)

Command (AWS CLI):

aws s3 ls s3://vulnerablebank-app --no-sign-request

Step-by-Step Guide:

  1. Check Public Access: If files are listed without auth, the bucket is misconfigured.

2. Exploit: Download sensitive files.

3. Mitigation: Set `BlockPublicAccess` and enforce IAM policies.

What Undercode Say:

  • Key Takeaway 1: Banking apps are high-value targets; test rigorously.
  • Key Takeaway 2: Automation (Burp, Nmap, JWT_Tool) speeds up testing.

Analysis:

The Vulnerable Bank App exercise highlights how easily attackers can exploit weak security controls. Financial institutions must prioritize secure coding, regular penetration testing, and zero-trust architecture. As AI-driven attacks rise, defenders must adopt AI-powered security tools to stay ahead.

Prediction:

With increasing fintech adoption, banking apps will face more sophisticated attacks. Organizations must integrate DevSecOps, automated scanning, and red teaming to combat evolving threats.

For the full write-up, visit: https://lnkd.in/dkNFEa3B

IT/Security Reporter URL:

Reported By: Appiahbismark During – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅

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