Microsoft fixes dangerous Notepad Markdown security bug on Windows 11

Microsoft fixes a remote code execution flaw in the modern Notepad app.
The bug involved improperly sanitized special characters in malicious Markdown (.md) files.
The incident fuels debate about adding AI and other unnecessary features to traditionally simple apps.
The vulnerability has been fixed with the February 2026 update availble through Windows Update and Microsoft Store.

Microsoft has fixed a new vulnerability in the modern version of the Notepad app that could have allowed attackers to take over your Windows 11 setup with a simple trick.

The issue, tracked as CVE-2026-20841, is a remote code execution flaw affecting the note-taking app, particularly when handling Markdown files. According to Microsoft’s Security Update Guide, the app failed to sanitize certain special characters embedded in crafted links properly. An attacker could create a malicious “.md” file and convince a user to open it.

If the user then clicked the embedded link, a script could launch, download additional payloads, and execute code on the system. In a successful scenario, the attacker could gain the same privileges as the logged-in user.

Microsoft says it hasn’t seen anyone actively exploiting the flaw in the wild. However, the severity was serious enough for the company to push a fix immediately as part of the February 2026 Patch Tuesday update.

What makes this case particularly interesting is the recent backlash around the Notepad’s evolution. Historically, the app was a minimal, offline text editor with virtually no attack surface beyond basic file handling.

However, now, the more features that get added, such as Markdown rendering enhancements and Copilot integration that relies on network connectivity, the more doors open to attacks.

Microsoft addressed the flaw through its February 10, 2026, security updates. The fix is available through Windows Update and the Microsoft Store app update mechanism. Users should install the latest cumulative updates and ensure Notepad is fully updated from the Store to patch the vulnerability.

Editorially, this incident reinforces a long-standing principle in software design. Simplicity is a security feature.

Notepad’s original best feature was its minimalism. As the software giant continues to modernize even its most basic tools, every new capability must be weighed against the associated risk. For example, features such as AI integration may offer convenience but also require a stronger security posture.

In all fairness, Notepad isn’t the only note-taking app with problems. Recently, the widely popular Notepad++ app has also been compromised by malicious actors. However, this was a hosting provider issue that allowed attackers to redirect users to malicious servers via compromised update manifests, and it was a problem with the application itself.

Since then, the developer has already switched providers and released an updated version of Notepad++ to improve security.