.NET Framework, the software framework developed by Microsoft that runs primarily on Windows, will have its 4, 4.5 and 4.5.1 versions deprecated in January 2016. This was already known, but Microsoft has now released another reminder through the official .NET blog.
Thus, starting from January 12, 2016 Microsoft will no longer provide support for NET 4, 4.5, and 4.5.1 frameworks, meaning that security updates, technical support or hotfixes will no longer be provided for these specific versions.
As for the other framework versions, 3.5, 4.5.2, 4.6 and 4.6.1, Microsoft said these will be supported for the duration of their established lifecycle. With this announcement, Stacey Haffner from Microsoft says “you should ensure that a supported version of the .NET Framework is installed in your environment, on Windows desktops and servers. This includes Azure and other cloud service deployments“.
If you recall, January 12 is also the same date when Microsoft is going to end support for all the older versions of Internet Explorer, as it tries to focus more on Microsoft Edge and bringing more people to Windows 10.
Thus, if you want to make sure that risks are minimized in your environment, Microsoft suggests to upgrade to a supported version, such as 3.5, 4.5.2, 4.6 and 4.6.1.