Microsoft hasn't paid much attention to Windows XP for years. But that all changed this week, after it revealed a nasty bug that could wreak havoc on the millions Windows XP users around the world.

Baked inside 79 security updates this week, Microsoft revealed that it needed to make an emergency patch to Windows XP. The company shared few details on the update, but said that the flaw it discovered in its nearly 20-year-old operating system is so concerning that its impact without a fix could be similar to the WannaCry ransomware attack that saw people around the globe have their data encrypted and forced to pay cash to hackers to get it back.

"Any future malware that exploits this vulnerability could propagate from vulnerable computer to vulnerable computer in a similar way as the WannaCry malware spread across the globe in 2017," Microsoft said in a statement. "It is highly likely that malicious actors will write an exploit for this vulnerability and incorporate it into their malware."

Microsoft didn't want to reveal much about how the bug works because it could give clues to hackers. But its description suggests that hackers exploiting the bug could take control of your computer, use it to encrypt your data and steal information, and ultimately force you to fork over hundreds or thousands of dollars to get it back. The flaw might also allow hackers to use your Windows XP machine as a tool to disseminate malware and target even more machines.

Suffice it to say that whatever this bug is, it's a scary one.

Who Cares About Windows XP?

Now, at first blush, you might be wondering why Microsoft would even care about Windows XP. After all, it's an operating system the company launched in 2001 and Microsoft hasn't been providing security updates and support on it for the last five years. Better yet, the bug Microsoft discovered wouldn't even affect any computer running Windows 8 or newer. So, if you have a Windows 10 machine, you're safe.

But there's a problem in Microsoft's operating system world.

As much as the company might want to push users to Windows 10, it's always had a rough time getting them to ditch Windows XP. And as of this writing, 3.6 percent of all Windows computers are running Windows XP, according to researcher Net Marketshare. With an estimated 1 billion Windows machines in use right now, that translates to 36 million computers around the world still running Microsoft's ancient operating system.

A Big Risk for Companies

Companies are especially at risk in this scenario and make up a large share of those Windows XP machines. That's because, in some cases, the mission-critical applications they use only work with Windows XP. So like it or not, they're forced to stay with Microsoft's old operating system.

In other cases, companies stick with Windows XP because they simply don't have the budget to deploy all new computers. In still other cases, they don't know enough about technology and the impact poor security can have on their company to care.

But the Windows XP patch suggests we all need to spend more time thinking about the technology we're using--and the technology we shouldn't be using. And if nothing else, it also means we need to be serious about updating our software with the latest security patches to keep ourselves and others safe.

That said, there's a slight problem in the latest Windows XP patch. Because Microsoft eliminated its Windows XP support years ago, there's no smooth method for updating the operating system with the new update. Instead, if you have a Windows XP machine, you need to go to this link to download the update. You'll then need to follow prompts to install it.

That's not the most user-friendly process. And it could also mean that many of those millions of XP machines might not get the update they need.

In other words, watch out.