Security Insights: Common API Security Mistakes and How to Avoid Them

Introduction

APIs are the backbone of modern applications. They connect mobile apps, web apps, cloud services, and even IoT devices. But with this power comes risk: APIs are often the easiest entry point for attackers.

Unfortunately, many companies still make avoidable mistakes in securing their APIs. Let’s look at the most common pitfalls — and how to fix them.

Mistake 1: Lack of Authentication & Authorization

• The Issue: Some APIs don’t properly verify who’s accessing them, or they allow over-permissioned accounts.
• The Risk: Attackers gain access to sensitive endpoints or escalate privileges.
• Fix:
  • Always enforce strong authentication (OAuth 2.0, OpenID Connect).
  • Implement least privilege access for API keys and tokens.

Mistake 2: Exposing Too Much Data

• The Issue: APIs often return unnecessary fields (e.g., sending full user profiles when only usernames are needed).
• The Risk: Sensitive data leaks like emails, PII, or internal IDs.
• Fix:
  • Follow the principle of data minimisation.
  • Use field-level filtering and never expose internal identifiers.

Mistake 3: Ignoring Rate Limiting & Throttling

• The Issue: APIs accept unlimited requests.
• The Risk: Opens doors to brute-force attacks and denial-of-service (DoS).
• Fix:
  • Implement rate limiting and quotas (e.g., 1000 requests per hour per user).
  • Use API gateways (AWS API Gateway, Kong, Apigee) for built-in throttling.

Mistake 4: Poor Input Validation

• The Issue: APIs trust input blindly.
• The Risk: Injection attacks (SQL, command, XML), corrupted data, or crashes.
• Fix:
  • Validate and sanitise all inputs.
  • Use strong schemas (e.g., JSON Schema, OpenAPI validation).

Mistake 5: No Encryption in Transit

• The Issue: APIs accept HTTP or don’t enforce TLS 1.2/1.3.
• The Risk: Attackers can sniff traffic and steal credentials.
• Fix:
  • Enforce HTTPS everywhere.
  • Regularly update SSL/TLS certificates.

Mistake 6: Weak Error Handling

• The Issue: APIs return detailed error messages (stack traces, SQL queries).
• The Risk: Attackers gain insights into backend systems.
• Fix:
  • Use generic error messages for clients.
  • Log details securely on the server side for debugging.

Pro Tip

Use an API Gateway + WAF (Web Application Firewall) as the first line of defense. They provide authentication, rate limiting, and logging out-of-the-box.

Takeaway

API security isn’t optional — it’s foundational. By avoiding these common mistakes (weak authentication, overexposed data, no rate limiting, poor input validation, lack of encryption, and weak error handling), you can significantly reduce your attack surface.

APIs are doors into your systems — make sure they’re locked, monitored, and reinforced.

References / Further Reading

• OWASP – API Security Top 10 (2023) (🔗 Link)
• RFC 6749 — OAuth 2.0 Authorization Framework (🔗 Link)
• Cloud Security Alliance — API Security Guidelines (overview) (🔗 Link)
• Center for Internet Security (CIS) — API Security Guide v1.0.0 (🔗 Link)