Introduction
APIs power today’s digital world — from mobile apps to large-scale cloud systems. But as their use grows, so does the number of attacks targeting them.
A single vulnerable API can expose sensitive data, compromise user accounts, or even bring down entire systems.
In this guide, I’ll explore the top 7 most common API security vulnerabilities, explain how they work, and — most importantly — show you how to patch and prevent them.
Whether you’re building with Laravel, Express.js, Django, or any other backend framework, these principles apply universally.
1. Broken Authentication
The problem:
When authentication isn’t properly implemented, attackers can impersonate users, steal sessions, or access restricted data. This often happens when tokens never expire, passwords aren’t hashed, or credentials are shared in plain text.
Example:
// ❌ Vulnerable: Token never expires
const token = jwt.sign({ id: user.id }, 'secret');
Patch it:
✅ Use time-limited, signed tokens (like JWT with expiresIn).
✅ Hash passwords using bcrypt or Argon2.
✅ Enforce strong password policies and rate limiting.
Secure Example:
const token = jwt.sign({ id: user.id }, process.env.JWT_SECRET, { expiresIn: '1h' });
Always store tokens in HttpOnly cookies to prevent XSS attacks.
2. Broken Object Level Authorization (BOLA)
The problem:
Attackers can manipulate object IDs in API requests to access or modify resources that don’t belong to them.
Example:
GET /api/users/123/profile // normal user
GET /api/users/124/profile // attacker changes ID
If your backend doesn’t check ownership properly, this leads to data leakage.
Patch it:
✅ Always validate user access based on their identity.
✅ Never rely solely on object IDs — verify ownership server-side.
Secure Example (Laravel):
if ($user->id !== $requestedUserId) {
abort(403, 'Unauthorized access.');
}
3. Excessive Data Exposure
The problem:
APIs sometimes return more data than necessary — including internal fields like passwords, tokens, or sensitive metadata.
Example:
{
"id": 1,
"username": "giftbalogun",
"password": "hashed_secret_here"
}
Patch it:
✅ Filter response data before sending it.
✅ Use serializers or DTOs to control what’s exposed.
Secure Example (Node.js):
const safeUser = _.pick(user, ['id', 'username', 'email']);
res.json(safeUser);
⚠️ 4. Lack of Rate Limiting
The problem:
Without rate limits, attackers can brute-force credentials or spam your API with thousands of requests per second — resulting in DDoS-like behavior.
Patch it:
✅ Implement rate limiting middleware (e.g., express-rate-limit or Laravel’s throttle middleware).
✅ Log suspicious behavior and block IPs that exceed limits.
Example (Express.js):
const rateLimit = require('express-rate-limit');
const limiter = rateLimit({ windowMs: 15 * 60 * 1000, max: 100 });
app.use('/api', limiter);
5. Injection Attacks (SQL, NoSQL, Command)
The problem:
When APIs accept unsanitized user input, attackers can inject malicious commands or queries into your system.
Example:
// ❌ Vulnerable to SQL injection
const result = db.query(`SELECT * FROM users WHERE id = ${req.params.id}`);
Patch it:
✅ Always use parameterized queries or ORM methods.
✅ Sanitize all input data.
Secure Example (Laravel Eloquent):
$user = User::where('id', $request->id)->first();
Even frameworks with ORMs can be exploited if you use raw queries incorrectly. Always validate user input.
6. Improper Error Handling
The problem:
Verbose error messages can leak internal system details, database names, or even stack traces — giving attackers clues about your setup.
Example:
Error: Cannot connect to MySQL server on 127.0.0.1:3306
Patch it:
✅ Use generic user-facing error messages.
✅ Log technical details privately.
✅ Implement centralized error handling.
Example (Express.js):
app.use((err, req, res, next) => {
console.error(err.stack);
res.status(500).json({ message: 'Something went wrong. Please try again.' });
});
7. Insecure Transport Layer (No HTTPS)
The problem:
If your API uses HTTP instead of HTTPS, sensitive data like passwords and tokens can be intercepted easily.
Patch it:
✅ Always use HTTPS — get free SSL certificates from Let’s Encrypt.
✅ Redirect all HTTP requests to HTTPS.
✅ Use secure headers with Helmet.js or Laravel’s middleware.
Example (Nginx redirect):
server {
listen 80;
server_name example.com;
return 301 https://$host$request_uri;
}
Bonus: Outdated Dependencies
Even a small outdated package can open huge security holes.
Regularly run:
npm audit fix
composer audit
pip install --upgrade
And use tools like Snyk or Dependabot to get vulnerability alerts early.
️ Conclusion
APIs are the backbone of modern software — but without proper security, they become the easiest attack vector.
By addressing these 7 vulnerabilities, you’re already ahead of 80% of developers who overlook them.
Security isn’t a one-time setup — it’s a continuous process.
Keep your dependencies updated, monitor your endpoints, and apply layered protection. Your users (and your future self) will thank you later.
Quick Recap
| Vulnerability | Patch |
|---|
| Broken Authentication | Use short-lived JWTs, strong passwords |
| BOLA | Enforce access control per resource |
| Data Exposure | Filter responses |
| No Rate Limit | Use throttling |
| Injection | Sanitize input, use ORM |
| Error Handling | Hide internal errors |
| Insecure Transport | Force HTTPS |