APIs are the connective tissue of modern software. They power mobile apps, third-party integrations, microservice communication, and public developer platforms. They also represent one of the most targeted attack surfaces in the current threat landscape.

The OWASP API Security Top 10 has become essential reading for any team that builds or consumes APIs. Let’s translate those vulnerabilities into concrete, actionable practices.

1. Implement Strong Authentication

Every API endpoint that handles non-public data requires authentication. OAuth 2.0 with short-lived JWT tokens is the industry standard. Key requirements:

  • Use short token expiry (15-60 minutes) with refresh token rotation
  • Never accept tokens in query strings — use the Authorization header
  • Validate token signature, expiry, issuer, and audience on every request
  • Implement token revocation for logout and security incidents

2. Enforce Authorization on Every Request

Authentication proves who you are. Authorization determines what you can do. These must be checked separately on every request.

// ❌ Wrong — relying only on auth
router.get("/users/:id/data", authenticate, (req, res) => {
  const data = db.getUserData(req.params.id); // Anyone can request any user ID!
  res.json(data);
});

// ✓ Correct — check ownership
router.get("/users/:id/data", authenticate, authorize, (req, res) => {
  if (req.user.id !== req.params.id && !req.user.isAdmin) {
    return res.status(403).json({ error: "Forbidden" });
  }
  const data = db.getUserData(req.params.id);
  res.json(data);
});

3. Implement Rate Limiting and Throttling

Without rate limiting, your API is vulnerable to brute force attacks, credential stuffing, and resource exhaustion. Implement rate limits at multiple levels:

  • Per IP address: Prevent volumetric attacks
  • Per API key / user: Prevent individual abuse
  • Per endpoint: Sensitive operations (login, password reset) need tighter limits

4. Minimize Data Exposure

APIs should return only the data required by the consumer. Never return entire database records and let the client filter — filter on the server.

“Excessive data exposure is one of the most common API vulnerabilities and one of the easiest to prevent. Return only what the caller needs, nothing more.” — OWASP API Security Project

5. Validate All Input

Never trust data coming from the client. Validate:

  • Data types (string, integer, boolean)
  • Format (email, UUID, date)
  • Length limits (prevent oversized payloads)
  • Allowed values for enumerated fields
  • Business rule validity (you can’t book a date in the past)

6. Use HTTPS Everywhere

This should go without saying in 2026, but APIs still get deployed without TLS. Every API endpoint must use HTTPS with modern TLS (1.2 minimum, 1.3 preferred). Enforce HSTS and reject HTTP connections at the infrastructure level.

7. Implement Comprehensive Logging

Log every API request with sufficient context for incident investigation:

  • Timestamp, request ID, method, path, status code
  • Authenticated user ID (not credentials)
  • Source IP address
  • Response time
  • Error details for failed requests

8. Use an API Gateway

An API gateway acts as the single entry point for all API traffic and provides centralized enforcement of authentication, rate limiting, logging, and threat protection. AWS API Gateway, Kong, and Apigee are popular options.

API security is not optional — it’s foundational. A single compromised endpoint can expose your entire data layer. Treat API security with the same rigor as your application and infrastructure security.