Microsoft has today released a quick update KB4135051 for the Windows 10 April update RTM Build 17134.1. This update brings Windows 10 Build 17134.5 along with itself and is available for insiders in Fast, Slow and Release Preview rings.
Are you on build 17134.1? If so, check for updates! KB4135051 is now published and will update you to 17134.5. This applies to all rings: Fast, Slow, and Release Preview. This is a quick download/install. Let us know how it goes!
— Windows Insider (@windowsinsider) April 27, 2018
This seems like a quick-fix update before the RTM Build 17134.5 starts rolling out to general public as Windows 10 April update. Microsoft just announced that Windows 10 April update will be available to download starting April 30.
You can read all the changes and new features that Windows 10 April update (Redstone 4) brings with itself by clicking here in our massive categorized changelog.