Windows 10 is the most current version of Microsoft’s flagship OS after launching two years.
However, despite this it is not the most popular Windows OS for PC fans.
According to NetMarketShare, Windows 7 is used by more PC users than Windows 10 – with the eight year-old OS having a 47.21 per cent market share.
This is compared to the second most popular PC OS, Windows 10, which has a 29.09 per cent chunk of the OS market share.
While Windows 8.1 and Windows XP have an operating system market share of around five per cent each.
However, for the huge amount of PC owners using an earlier version of Windows – they’ve been given a stark warning as to why they need to upgrade to Windows 10.
The Register has reported that Microsoft have been patching out security bugs in Windows 10 but NOT immediately rolling those out to Windows 7 and 8.
This lag in updates leaves potentially hundreds of millions computers at risk of an attack.
Exploits that hackers and malware are taking advantage of is being fixed in the big Windows 10 releases.
However, this is slowly filtering back to Windows 7 and 8 in the form of monthly software updates.
This was revealed by researchers on Google’s Project Zero team.
It’s feared cybercriminals comparing the various builds of Windows will notice these holes in earlier versions and take advantage of it.
Google researchers outlined their fears in a blog post.
Google Project Zero researcher Mateusz Jurczyk said: “Microsoft is known for introducing a number of structural security improvements and sometimes even ordinary bug fixes only to the most recent Windows platform.
“This creates a false sense of security for users of the older systems, and leaves them vulnerable to software flaws which can be detected merely by spotting subtle changes in the corresponding code in different versions of Windows.”
Jurczyk added that by broadly upgrading security defences in Windows 10, it’s making it easier hackers to see where the weak spots are in older versions.
He said: “Not only does it leave some customers exposed to attacks, but it also visibly reveals what the attack vectors are, which works directly against user security.”
A Microsoft spokesperson said: “Windows has a customer commitment to investigate reported security issues, and proactively update impacted devices as soon as possible.
“Additionally, we continually invest in defense-in-depth security, and recommend customers use Windows 10 and the Microsoft Edge browser for the best protection.”