Today, Microsoft released Windows 10 Insider Preview Build 17134 (Redstone 4) to insiders on the fast ring. This build does not contain any new features, but rather acts as a new build with security updates included that fix the vulnerabilities from KB4100375.
KB4100375 fixed the following vulnerabilities discovered in Redstone 4 before it was released:
Microsoft's insider build announcement states:
Today, we are releasing Windows 10 Insider Preview Build 17134 (RS4) to Windows Insiders in the Fast ring. This build has no new features and includes the fixes from KB4100375 as well as some fixes for general reliability of the OS. As Build 17133 progressed through the rings, we discovered some reliability issues we wanted to fix. In certain cases, these reliability issues could have led to a higher percentage of (BSOD) on PCs for example. Instead of creating a Cumulative Update package to service these issues, we decided to create a new build with the fixes included. This just reinforces that Windows Insiders are critical to helping us find and fix issues before releasing feature updates to all our customers so thank you!
There is still no word as to whether the blocking bug was fixed that was preventing the release of Redstone 4, otherwise known as the "Spring Creators Update".