The Next.js Security Wake-Up Call for Vibe Coders Everywhere

It’s Monday morning. You’ve barely opened your eyes and suddenly remember that you promised to build a brand-new app by the stakeholder meeting this afternoon. In any sensible world, this would be a recipe for disaster. But now, we have something different — something called “vibe coding.”

You simply mutter your wish for “a frictionless e-commerce platform with user-authentication and real-time chat,” and poof, like magic, the AI generates the entire codebase.

Need a fancy UI? With another passing thought, another chunk of polished code appears. After all, who has time to worry about syntax when you can vibe your way to a finished product?

But here’s the catch: as the excitement around “vibe coding” continues to grow, an unsettling question surfaces — what happens when we no longer truly understand the inner workings of our code?

This worry recently became all too real with the discovery of a significant security vulnerability in Next.js, a hugely popular React framework.

Astonishingly, a single, deceptively simple HTTP header could disable critical middleware checks entirely — turning thousands of meticulously crafted websites into open targets overnight. The loophole boiled down to mismanaging how Next.js tracks repeated calls to its middleware, effectively allowing any attacker to trick the system into skipping security checks.

If you’re running a Next.js application, here’s how to fix or mitigate the risk right now:

1. Upgrade to the latest version, which should be >=15.2.3

2. If you can’t update right away, temporarily block the vulnerable header at your web server level like this:

Let’s be clear, this vulnerability wasn’t caused by “vibe coding”. It was a case of an honest mistake... unfortunately just in a widely used framework.

However, all developers should take note:

When a popular framework like Next.js ships with a major vulnerability, it underscores the dangers of shipping code we haven’t deeply inspected. Even if the problem is in a third-party library, we need people who truly understand how that library works — or at least have the diligence to spot something that looks suspicious.

Therefore, if we embrace a coding style that relies on AI to handle the nitty-gritty without truly understanding those details ourselves, who makes sure our house of cards doesn’t come crashing down in the future?

In this newsletter:

• We’ll first explore how “vibe coding” burst onto the scene — tracing its origins, celebrating its playful spirit, and examining early success stories that captivated developers everywhere.

• Next, we’ll examine cautionary tales, highlighting the pitfalls of trusting automated code without knowing the specifics of what it does.

• Finally, we’ll circle back to discuss the real limitations of “coding by vibes,” underscoring why strong foundational knowledge has become more critical than ever in today’s rapidly evolving AI-driven landscape.

Let’s get started.