Many Reddit users faced an unexpected behavior from Windows Update when suddenly it forcibly and silently started the installation process for Windows 10 without any warning. This happens if KB3035583 is installed, which comes with the following description:
Update installs Get Windows 10 app in Windows 8.1 and Windows 7 SP1
Without any confirmation, the updated Get Windows 10 app not only starts setup but upgrades the user's installed operating system to Windows 10!
While Microsoft officially claimed several times that such behavior will never be implemented and that the user will retain the choice, a significant number of Reddit users says that it is not true.
The mentioned KB3035583 automatically unhides itself periodically when you have hidden it and installs the updated GWX (Get Windows 10) app. The GWX app should ask the user if he wants to upgrade his operating system, after checking that the computer's hardware is compatible with Windows 10 and fits its system requirements.
According to the Reddit discussion, it is possible to "fix" the "mad" GWX app by uninstalling KB3035583 which resolves the issue and returns the upgrade process back to the user-driven procedure.
Here are a few examples from the Reddit topic:
You can join the discussion here: reddit.
There is no official information or confirmation of this issue yet.