Microsoft's using Windows Update to force Windows 10 ads onto older PCs:

Microsoft is installing an update on Windows 7 and 8 machines which will push users to upgrade toWindows 10.

The update – KB 3035583 – is vague about its purpose. The official description states:

This update enables additional capabilities for Windows Update notifications when new updates are available to the user. It applies to a computer that is running Windows 8.1 or Windows 7 Service Pack 1 (SP1).

But what are those "additional capabilities"? Installing the update – which is marked as "Recommended" – on a machine running Windows 8.1 leads to the creation of four new folders in the Windows\WinSxS folder, prefixed "amd64_microsoft_windows_gwx". The description of one of the files installed – GWXUXWorker.exe – is "Get Windows 10".

Another file of interest is config.xml. This has sections for various phases, starting at <Phase name="None"> and continuing through AnticipationUX, Reservation, Reserved, RTM, GA, various Upgrade phases, and, finally, UpgradeSetupFailed.

There is also a reference to an OnlineAdUrl, presumably a page hyping the benefits of Windows 10, though this is currently a dead link. The update appears to be intended to advertise Windows 10 and push the user towards consenting to download and install it.

However, this raises questions over user consent to receive the update in the first place. The update is classified as "Recommended", which means that users may receive it automatically, depending on their Windows Update settings. This is the middle classification, between Important (which includes material such as security patches) and Optional (never installed automatically).