Microsoft has temporarily pulled the Windows 8.1 Update from its Windows Server Update Services (WSUS) platform due to an issue that can cause the OS to ignore future patches. The issue only affects servers running encrypted HTTPS connections, therefore the update is still rolled out to consumer.
: Microsoft has pulled the update from its WSUS platform, which allows for distribution of approved software patches within an internal network, following reports of a serious flaw. When installed on a Windows 8.1 system, the computer loses the ability to check the WSUS server for future updates.
Although the flaw only affects servers running encrypted HTTPS connections, which is not the default, but with the latest TLS 1.2 functionality disabled, which is the default, the flaw is serious enough for the update to be removed from distribution. Although it will still be available through Windows Update for home users, WSUS administrators are asked to wait for an updated version to be released; those who have already deployed the flawed update can either enable TLS 1.2 if running WSUS on Windows Server 2008 R2 or disable HTTPS altogether if running on any other platform.
Please keep in mind that Windows 8.1 Update is a mandatory update for Windows 8.1 users, if you don't install this update you will not receive future updates from Microsoft.