Google He discovered a security vulnerability in Windows 10 S, the version of Windows 10 that Microsoft lists as the safest because it restricts users from using Win32 applications. The security loophole allows arbitrary code execution on devices with Device Guard enabled, but according to a post by Neowin, successful exploitation requires access to the system.
The vulnerability has been discovered by the Google Project Zero program that gives stakeholders a 90 days deadline to troubleshoot their software. But Microsoft seems to have requested an extension on the deadline after releasing a vulnerability update in January.
The company then prepared a fix for April, but apparently could not finish it, asking for a deadline by May. However, Google refused to postpone another postponement of the vulnerability, and from now on all the details are released online.
The Windows 10 S bug is particularly difficult to exploit, but if the "safest Windows system" manages to do so, go for a walk.
Windows 10 S does not allow the installation of Win32 software and Microsoft allows you to upgrade to Windows 10 Pro directly through the operating system. However, the mood of Windows 10 S as autonomous functional will soon stop and will be integrated into Windows 10 as "S Mode".
So although Microsoft has promised a patch on May 3rd Patch, it's not sure it will be released as the plan is to integrate the operating as a function into the main OS of the company, namely Windows 10.
If you are interested in more technical details and want the PoC vulnerability you will find it on its announcement page Project Zero of Google.