My First Security Incident

The Support Ticket

It was a Tuesday morning. I was drinking coffee and going through support tickets. One caught my attention:

My first thought was user error. Maybe they logged into the wrong account? But as I read it again, a cold feeling spread through my chest.

I opened my laptop and tried to reproduce the issue. It took me about three minutes to confirm it was real.

What Went Wrong

The bug was embarrassingly simple. I had a function that loaded user data based on a URL parameter:

The function checked if the user was logged in. But it didn't check if the logged-in user matched the user_id in the URL. Any authenticated user could view any other user's dashboard by changing the number.

I'd written this code at 2 AM during a launch crunch. I remember being tired and thinking "I'll add proper auth checks later." That "later" never came.

The Panic Response

I made several mistakes in my initial response:

Mistake 1: Fixing Before Investigating

My first instinct was to fix the code immediately. I pushed a fix within 20 minutes. But I should have first investigated how long the vulnerability existed and whether it had been exploited.

Mistake 2: Not Documenting

I didn't take screenshots or save logs before making changes. When I later needed to understand the scope of the incident, I had limited information.

Mistake 3: Delaying Customer Communication

I waited three days to respond to Mark's ticket because I was "still investigating." He deserved a faster acknowledgment, even if I didn't have all the answers.

What I Should Have Done

Looking back, here's the proper incident response sequence:

1. Acknowledge the report immediately, even just to say "we're investigating"
2. Document everything before making any changes
3. Assess the scope: How long has this existed? What data was potentially exposed? Any evidence of exploitation?
4. Implement a fix with proper review (not panic-coded)
5. Communicate with affected users based on what you found
6. Post-mortem: How did this happen and how do we prevent similar issues?

The Investigation

After calming down, I dug into the logs. The vulnerability had existed for 6 weeks. During that time:

• Zero evidence of anyone systematically exploiting it
• Two instances where users might have accidentally seen other data (both appeared to be URL copy/paste errors)
• No sensitive financial data was exposed (that was in a separate, properly secured system)

I got lucky. If someone had been actively looking for vulnerabilities, they would have found this easily.

The Conversation with Mark

I called Mark directly to explain what happened. It was uncomfortable, but it was the right thing to do.

His response surprised me: "Thanks for being honest. I've used apps where weird stuff happened and no one ever explained anything. I appreciate you telling me what went wrong and what you fixed."

He stayed a customer. That conversation taught me that transparency, even about failures, builds trust.

What Changed After

Code Review for All Auth Logic

Any code that touches authentication or authorization gets reviewed by at least one other person. No exceptions, no matter how simple it seems.

The "2 AM Rule"

I don't ship code after midnight anymore. Tired coding leads to exactly these kinds of mistakes. If it's that urgent, it can wait until morning when I can think clearly.

Authorization Tests

I added automated tests that specifically try to access resources as the wrong user. If User A can see User B's data, the test fails.

Incident Response Plan

I wrote down a simple incident response checklist. When something goes wrong, I don't have to think about what to do. The process is documented.

For Other First-Time Founders

If you haven't had your first security incident yet, you will. Here's what I wish I'd known:

• It's going to feel terrible. That's normal. Don't let the shame paralyze you.
• Document before you fix. You need to understand the scope before you can properly respond.
• Communicate honestly. Customers can handle bad news. They can't handle feeling deceived.
• Use it as a learning moment. Every incident should result in process improvements.
• Don't build alone. Have someone else review security-critical code.

The best time to prepare for an incident is before it happens. The second best time is right after your first one.