The AI Agent That Almost Cost Me a Security Breach

The Setup

A few weeks ago, I was working on a microservices learning project. I’d built most of the services already—User, Product, Cart, Order. The last critical piece was the API Gateway: the single entry point for all client requests.

I’d documented everything:

• The routes
• The authentication flow
• The middleware for authorization
• The role-based access control (RBAC) logic

Then I made a decision: Let an AI agent write it.

I fed it all the specifications, watched it generate the code, and when I saw tests passing with green checkmarks, I felt… productive. Fast. Like I’d leveraged the power of AI to move quickly.

Everything looked correct.

The Bug That Almost Got Away

The API Gateway worked. Requests came in, got routed properly, returned the right status codes. For days, I didn’t notice anything wrong.

Until I decided to test something specific:

What happens if an unauthorized user tries to access an admin endpoint?

I sent a request with limited permissions for an action only admins could perform.

The response came back: 403 Forbidden. ✓

But then I checked the database.

The action had executed anyway.

Data had been modified. The authorization check had failed, but the code kept running.

That’s not a bug. That’s a security breach.

The Root Cause

I pulled up the code the AI had generated:

func AuthorizeAction(requiredRole string) gin.HandlerFunc {
  return func(c *gin.Context) {
    userRole := c.GetString("role")
    
    if userRole != requiredRole {
      c.JSON(http.StatusForbidden, gin.H{"error": "unauthorized"})
    }
    
    // Continue to next handler
    c.Next()
  }
}

Do you see it?

When the authorization check fails, the middleware sends a 403 response. But there’s no return statement. The code continues executing. The c.Next() call happens anyway, passing control to the actual handler.

The error response was sent to the client. But the request still went through.

This is a classic authorization bypass. And it’s terrifying.

Why This Matters

If I hadn’t understood the flow deeply:

• If I hadn’t reviewed the logic carefully:
• If I’d just trusted the AI and deployed this:

This would be production data leakage.

Attackers would see a 403 and think they were blocked. Meanwhile, their malicious requests would silently succeed.

The Lesson

This experience crystallized something I’d been thinking about:

AI is an extraordinary tool. But it’s not a replacement for understanding.

The AI can:

• Write code faster than I can type
• Generate boilerplate without tedium
• Explore ideas I might not have considered
• Accelerate my work by orders of magnitude

But the AI cannot:

• Take responsibility for security
• Understand the business consequences of bugs
• Review its own work
• Know what “correct” means in your specific context

The Real Risk

In monoliths, a bug like this might affect one feature. It’s discoverable through testing.

In microservices, a single missing return statement in the API Gateway becomes a single point of failure. It’s the gatekeeper. Everything flows through it.

A small mistake scales to a catastrophic breach.

How To Use AI Responsibly

I still use AI for code generation. It’s faster. But now I approach it differently:

1. Understand the problem deeply before asking for help
2. Review the generated code against your mental model of correct behavior
3. Test edge cases, especially security boundaries
4. Assume the AI made mistakes—because it will
5. Take responsibility for what you ship, not the tool that helped you build it

The Harder Truth

This wasn’t the AI’s fault. It’s a very common pattern to forget a return statement in middleware. I’ve seen it in human-written code, too.

But here’s what’s different:

When a human writes code, they own it. They understand it. They review it before it goes to production.

When you delegate to AI without understanding, you’re creating a false sense of security. You think the tool knows what it’s doing. You think passing tests means the code is correct.

It doesn’t always. Not even close.

Moving Forward

I fixed the code. One line: return after the 403 response.

if userRole != requiredRole {
  c.JSON(http.StatusForbidden, gin.H{"error": "unauthorized"})
  return  // THIS WAS MISSING
}

And I learned something that goes beyond this one project:

Tools amplify your judgment—they don’t replace it.

Use AI. Use it aggressively. Let it speed you up. But never let it replace your understanding.

In systems that matter—especially distributed systems where failures cascade—your brain is the last line of defense.

For other engineers: Have you caught an AI-generated bug like this? What’s the worst one you’ve seen? I’d love to hear your stories—they’re the real education.

Tags: #Security #Microservices #AI #Authorization #SoftwareEngineering #Lessons #BackendDevelopment