If you are running an older Windows system Windows 2000, Vista, XP, Windows 2003, Windows 2008, or Windows 7 you can go here for a security patch, the patches are all listed as critical.
True, in this instance, but both have numerous vulnerabilities of their own with this month's patches listing 15 critical vulnerabilities, 11 of which are for the IE11 and Edge web browsers.
If you are one of the very many people still using older versions of Windows please give serious consideration to upgrading. Windows 2000 and XP are well and truly unsupported. There actually never was a Windows 2003 or 2008 for the desktop, they were both server only versions but are nevertheless also unsupported. Windows 7 reaches end-of-life (read: unsupported) for most installations on 14th January 2020.
The fact that Microsoft has a few times released emergency patches for unsupported versions is an indication of both the severity of the issue and an acknowledgement of the many such systems still in use. BUT you will not receive those patches automatically. You have to go to their download site and fetch and install them manually. This does of course mean you have to know about them in advance and unfortunately such information is rarely issued via the mass media.
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'In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual.' - Galileo Galilei