We Audited a Vibe-Coded Fintech App — Here's What We Found

Why We Ran This Audit

AI coding tools like Lovable and Replit Agent have made it possible for non-technical founders to build a working app in days instead of months. That's genuinely useful — but for fintech specifically, "it works" and "it's safe to launch" are two very different bars. A founder came to us with an AI-generated MVP for a personal finance app and asked us to review it before their beta launch. What we found is a pattern we're now seeing across most vibe-coded fintech products.

What We Found

No CSRF protection. The app had no cross-site request forgery safeguards on any state-changing endpoint — meaning an attacker could potentially trigger actions on a logged-in user's behalf without their knowledge.

Missing security headers. Standard headers like Content-Security-Policy and X-Frame-Options were absent, leaving the app more exposed to injection and clickjacking attacks than it needed to be.

Exposed secrets in client-side code. API keys for third-party financial data providers were embedded directly in the frontend bundle, visible to anyone who opened developer tools.

Weak session handling. Session tokens weren't rotating on privilege changes, and there was no mechanism to invalidate sessions after a password reset — a basic but critical control for any app handling money.

No input validation on transaction amounts. The backend trusted values sent from the client without server-side revalidation, which is one of the most common ways financial apps get exploited.

None of this is unusual for AI-generated code. It's not that the tools are bad — they're optimized for speed and functional correctness, not for adversarial thinking about what a malicious user might try.

What We Did About It

We didn't rebuild the app from scratch. Most of the AI-generated UI and business logic was genuinely solid, and rewriting it would have wasted the speed advantage vibe coding gave the founder. Instead, we:

• Added server-side validation on every financial transaction endpoint
• Implemented CSRF tokens and proper security headers
• Moved all secrets into a backend-only environment with a proxy layer for third-party API calls
• Rebuilt session management with proper rotation and invalidation
• Ran a full penetration test before sign-off

The founder kept their timeline. They just launched with a product that could actually survive contact with real users and real money.

The Bigger Pattern

This isn't a one-off. Recent scans of production vibe-coded applications have found the majority carrying real security issues, including exposed secrets and missing CSRF protection, at rates far higher than traditionally engineered software. For a to-do list app, that's a bug. For a fintech app, that's a breach waiting to happen.

If you've built an MVP with AI tools and you're preparing to handle real user data or real money, get it audited before launch. It's a fraction of the cost of a breach — and often a fraction of the cost of the build itself.