Microsoft Has Patched a Serious Vulnerability in This Popular Windows Application.
Artificial intelligence-based changes to Notepad (yes, that Notepad) allowed attackers to execute arbitrary code on your computer. The vulnerability was related to Markdown support, which was added last year. Markdown is a simple way to add formatting, including links, to text documents, and it was links that were the source of the vulnerability.
“An attacker could trick a user into clicking a malicious link inside a Markdown file opened in Notepad, causing the application to run untrusted protocols that download and execute remote files,” the security advisory states.
Markdown has long been popular in certain segments of the internet—anyone who occasionally comments on Reddit or chats on Discord is likely at least somewhat familiar with it. But the markup language has become even more important in the age of artificial intelligence—most documents are converted to plain text Markdown files for training models.
Microsoft is fixing more bugs than ever in Windows 11.
Markdown support was added around the same time Copilot was integrated into Notepad , as part of a broader strategy to embed AI into every corner of the operating system. And it’s arguable that all these AI additions are introducing new vulnerabilities. According to Krebs on Security , a prominent cybersecurity blog, Microsoft will fix 1,129 bugs in 2025. This is an 11.9% increase from the previous year, which was already an unusually high figure. Microsoft itself acknowledges that AI agents will uncover new vulnerabilities , even as the company adds them to Windows.
All of this suggests that installing security updates is probably more important now than ever. While you can disable all AI features in Windows , that’s unlikely to protect you from all new vulnerabilities—although installing Linux might.
How to fix this vulnerability in Notepad
Fortunately for Windows users, this vulnerability was fixed in Microsoft’s February 2026 security update . To see if it’s installed, open the Settings app, go to Windows Update, and check if there’s a pending update labeled “Security Update 2026-02.” If so, click “Restart now” to install the update.