https://wccftech.com/windows-10-2019-build-windows-sandbox/

After issuing an emergency patch to various versions of Windows, Microsoft has now released a fresh new Windows 10 2019 Preview build to Insiders in the Skip Ahead and Fast ring. Today’s is the last major build of 2018 but there could be a cumulative update being issued in the next couple of weeks, Dona Sarkar and Brandon LeBlanc wrote in today’s blog post.

Since this is the last major WIP build, it is no surprise that Windows 10 Insider Preview Build 18305 is coming with quite a long list of features, including a new Windows Sandbox.