Effective immediately, users running Windows 10 version 1511 and below will not receive any further security updates. In order to verify what version of Windows 10 you are running, type "winver" into the search box and press Enter. The dialog box that appears should list a version number. This change affects the following editions of Windows 10:
- Windows 10 Home
- Windows 10 Pro
- Windows 10 Education
- Windows 10 Enterprise
Version 1151 codenamed Threshold 2 was released in November of 2015. The latest version 1703 known as the Creators Update is set to be supported through October 13, 2020, although the second Creators Update is right around the corner set to be released on October 17.
If you are affected by this change and somehow managed to avoid running Windows 10 automatic updates, it is advised that you upgrade as soon as possible to a newer version in order to continue receiving security patches.