From Vulnerable to Secure: How ESM Global Consulting Transforms API Security

APIs are the backbone of modern enterprises, enabling seamless integration between applications, services, and users. But with this connectivity comes risk—SQL injection (SQLi), authentication flaws, and misconfigurations can turn an API from a business enabler into a security liability.

At ESM Global Consulting, we specialize in Digital & Physical Red Teaming, Cloud & Database Security, and API Hardening to protect businesses from cyber threats. This case study highlights how we transformed a vulnerable API for a fintech client, eliminating security risks and ensuring compliance with industry best practices.

Table of Contents

1. The Challenge: A Fintech API Under Attack
   1. Client Profile
   2. Security Issues Discovered
2. The Solution: ESM Global’s 5-Step API Security Transformation
   1. Step 1: SQL Injection Mitigation
   2. Step 2: Strengthening Authentication & Access Control
   3. Step 3: Preventing Data Leaks & Implementing Encryption
   4. Step 4: Securing API Endpoints & Implementing Rate Limiting
   5. Step 5: Continuous Monitoring & Security Testing
3. The Result: A Secure, Compliant, and Scalable API
4. Conclusion: Secure Your APIs with ESM Global Consulting

The Challenge: A Fintech API Under Attack

Client Profile

A fast-growing fintech startup relied on APIs to facilitate real-time payments, user authentication, and financial data retrieval. Their REST API, built on Node.js with PostgreSQL, was central to their business operations.

Security Issues Discovered

During an initial assessment, we uncovered multiple critical vulnerabilities, including:

1. SQL Injection (SQLi) Risk

   • Directly concatenated SQL queries in multiple endpoints.

   • No input validation or sanitization for user data.

2. Broken Authentication & Authorization

   • Weak API key security—some keys were exposed in frontend JavaScript.

   • No proper role-based access control (RBAC) for sensitive endpoints.

3. Excessive Data Exposure

   • API responses contained sensitive user data, such as hashed but weakly salted passwords and transaction history.

4. Unsecured API Endpoints

   • No rate limiting, making the API susceptible to brute-force attacks.

   • CORS misconfiguration, allowing requests from any domain.

The client was at risk of data breaches, compliance violations, and financial fraud if these issues were exploited.

The Solution: ESM Global’s 5-Step API Security Transformation

Step 1: SQL Injection Mitigation

We replaced all raw SQL queries with parameterized queries and prepared statements, preventing SQLi attacks.

Before (Vulnerable Code):

db.query("SELECT * FROM users WHERE username = '" + username + "' AND password = '" + password + "'");  

After (Secure Code):

db.query("SELECT * FROM users WHERE username = $1 AND password = $2", [username, password]);  

🔹 Outcome: Eliminated SQLi risk by ensuring user input was safely handled.

Step 2: Strengthening Authentication & Access Control

• Replaced API keys with OAuth 2.0 tokens, adding token expiration and refresh mechanisms.

• Implemented Role-Based Access Control (RBAC) to restrict sensitive actions based on user roles.

• Hardened password security by enforcing bcrypt hashing with strong salts.

🔹 Outcome: Secure authentication and granular control over API access.

Step 3: Preventing Data Leaks & Implementing Encryption

• Masked sensitive data in API responses (e.g., showing only the last 4 digits of account numbers).

• Forced HTTPS for all API traffic, preventing man-in-the-middle attacks.

• Implemented encryption at rest for stored data using AES-256.

🔹 Outcome: Enhanced data protection and compliance with GDPR & PCI-DSS.

Step 4: Securing API Endpoints & Implementing Rate Limiting

• Added API Gateway Protections:

  • AWS API Gateway with request validation and WAF (Web Application Firewall).

  • Cloudflare WAF to block malicious payloads.

• Implemented Rate Limiting:

  • Limited login attempts to 5 per minute to prevent brute-force attacks.

  • Capped API requests per user to 100 requests per minute to prevent abuse.

🔹 Outcome: API endpoints became resilient to abuse and automated attacks.

Step 5: Continuous Monitoring & Security Testing

• Integrated API Security Scanning with tools like OWASP ZAP & Burp Suite.

• Deployed real-time monitoring with SIEM solutions (Splunk, ELK Stack).

• Set up alerts for suspicious activities like unusual login attempts or high API traffic spikes.

🔹 Outcome: Proactive threat detection and rapid response capabilities.

The Result: A Secure, Compliant, and Scalable API

🚀 Key Success Metrics:
✅ 100% SQL Injection Mitigation – No exploitable injection points found post-remediation.
✅ 99.99% API Uptime – No security-related downtime after security hardening.
✅ Compliance with PCI-DSS & GDPR – Passed a third-party compliance audit.
✅ 0 Unauthorized Data Exposures – API responses contained only necessary data.

Client Feedback:
"Before working with ESM Global Consulting, we knew security was a concern but didn’t realize how vulnerable we were. Their structured approach and expertise not only secured our API but also gave us the confidence to scale securely."

Conclusion: Secure Your APIs with ESM Global Consulting

APIs power modern businesses, but without proper security, they become a gateway for attackers. At ESM Global Consulting, we specialize in securing APIs, cloud environments, and databases, ensuring that your applications remain resilient, compliant, and secure.

Need to Secure Your APIs?

🔒 Contact us today for an API security assessment and safeguard your business against cyber threats.