A blog posted in the Premier Field Engineering Platforms section of http://blogs.technet.com revealed that Microsoft made it clear that all Windows 8.1 users will have to install the new update released yesterday to continue receiving security patches and other updates. These are extremely important to keep computers safe from viruses and security threats.
Updating Windows 8.1 should not be a matter of concern since the update is available through the regular Windows Update method. Thus, the update would download and install automatically unless you have turned off automatic updates for some reason. It is better to enable automatic update and allow Microsoft to update your OS. There is no way to skip this process and still hope to receive security patches.
To see whether you are using Windows 8 or 8.1, you need to go to PC Settings> PC and devices> PC info and check the “Windows” section. At any point of time, if you want to update Windows 8 to 8.1, you need to visit the Store app and click on the update option noticeable on the home page itself.
Windows 8, Windows 7 and Windows Vista users need not worry about any kind of update since Microsoft would continue to send patches as usual. As far as Windows XP users are concerned, they should upgrade their OS to a newer version as Microsoft has ended its support towards XP yesterday.