Fears of a massive global computer virus outbreak have prompted Microsoft to issue security updates for very old versions of its Windows software.
One patch is for Windows XP, which debuted in 2001 and Microsoft stopped supporting in 2014.
Microsoft said the patch closed a hole that could be used to spread a virus.
Malicious hackers exploiting it could kick off a worldwide outbreak like the 2017 WannaCry worm, which hit thousands of machines.
It was "highly likely" the vulnerability would be exploited if it went unpatched, wrote Simon Pope, Microsoft's director of incident response, in a blog about the bug.
He said the bug could be exploited simply by connecting to a vulnerable machine over the internet.
"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," he said.
This danger prompted the release of a patch that closes the loophole in:
Windows Server 2008
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