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Windows Sandbox broken in Insider build 18305.1003

A small cumulative update has broken one of Windows 10 preview build 18305's biggest features.

On December 20, Microsoft shipped an Internet Explorer security fix to the latest Windows 10 Fast ring Insider build, bringing it up to build number 18305.1003. In an update to the build's list of known issues, Microsoft this week confirmed that the fix also had the effect of breaking both Windows Defender Application Guard and Windows Sandbox (via OnMSFT).

From the release notes:

  • [ADDED 1/1/19] Windows Defender Application Guard and Windows Sandbox fail to launch on Build 18305 with KB4483214 installed. Workaround is to uninstall this update.

Presumably, Microsoft will have a fix for the issue in its next Fast ring release, but uninstalling the cumulative update is, for now, the only workaround.

Build 18305 brought with it a number of interesting new features, but Windows Sandbox is potentially one of the biggest surprises. The feature allows you to fire up a clean, virtual desktop environment through which you can run and test untrusted software without worrying about its impact on your base installation. Once Windows Sandbox is closed, all of its files and software are permanently deleted.

Dan Thorp-Lancaster is the Editor in Chief for Windows Central. He began working with Windows Central as a news writer in 2014 and is obsessed with tech of all sorts. You can follow Dan on Twitter @DthorpL and Instagram @heyitsdtl. Got a hot tip? Send it to

  • It didn't work on my Surface Pro 2017 even before that security update. I hope the overall functionality will be addressed and not just the issues caused by the update.
  • Damn, I was looking forward to this functionality I hope it's fixed soon. Unless they have stopped flooding you with updates the moment you install a fresh insider build and connect to the internet - I doubt they have... because it sort of defeats the purpose of general use testing....
  • Can sandbox be used for online gaming? Lots of people are reporting that their accounts are being locked for "allegedly" having cheating software installed. Running games in a sandbox that provides a totally vanilla version of Windows could be the answer to overly-twitchy anti-cheat mechanisms. Give them a totally pure version of windows with nothing else in it. Or would this just be too slow, like running a game in a VM?
  • That depends on what resources are allocated to a sandbox and if we can alter / increase resources used. My guess is it would be a standard VGA driver to provide a complete sandbox experience, unless it creates instances using the archived drivers - which is updated when new drivers are installed - thus allowing WIndows to automatically reinstall drivers when uninstalled via device manager - if the delete driver option is not selected.