Windows 10 update causes critical security flaw: Here's an (easy) fix

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Windows 10 has a serious security vulnerability that prevents Windows Sandbox and Windows Defender Application Guard — a pair of tools crucial in keeping your laptop secure — from opening. 

At least, this would be a serious concern if there wasn't an effortless solution: restarting your PC. But more on that later, let's talk about why this is such a scary flaw. 

For those who don't know, Windows Sandbox lets Windows 10 users run applications within an isolated desktop environment, away from a host machine. That's important because if you run a malicious app in Windows Sandbox, it can't access the personal files stored on your main machine.

The other app, Windows Defender Application Guard, was designed for the Microsoft Edge browser as a safeguard for enterprise users against untrusted websites. 

These are protections you want operating at full capacity on your system to ensure it's protected from bad actors. Unfortunately, laptops running Windows 10 Pro and Enterprise versions 1903, 1909 and 2004 are affected by the issue that is preventing these tools from operating properly, according to Microsoft's own support documents (as reported by Bleeping Computer and Techdows).

What to do now

If your system is affected by the bug, you'll see a pair of error notifications after the two apps fail to start. 

  • E_PATHNOTFOUND (0x80070003)

The simple fix? Restart your laptop. Microsoft says that the tools will load properly once you do so. 

Yes, it's really that easy, but there is one caveat: the solution isn't permanent. That means you might need to restart your system more than once, which can become annoying and disruptive. The good news is that Microsoft is hard at work on a permanent fix that should be pushed through a future software update. 

Our best advice is to wait patiently for Microsoft to release its patch for this frustrating security vulnerability. When you see the two error messages, don't ignore them. Instead, restart your system as soon as possible so the two apps can protect you from malicious attacks.

Phillip Tracy

Phillip Tracy is the assistant managing editor at Laptop Mag where he reviews laptops, phones and other gadgets while covering the latest industry news. After graduating with a journalism degree from the University of Texas at Austin, Phillip became a tech reporter at the Daily Dot. There, he wrote reviews for a range of gadgets and covered everything from social media trends to cybersecurity. Prior to that, he wrote for RCR Wireless News covering 5G and IoT. When he's not tinkering with devices, you can find Phillip playing video games, reading, traveling or watching soccer.