Beware of opening unknown documents. Don’t even Preview them.

Microsoft says hackers are exploiting a vulnerability in ALL versions of Windows that lets them hijack users' computers — and there's currently no fix

• The flaw emerges from the way that Windows handles and renders fonts
• Hackers can exploit it by tricking users into opening a malicious document
• Microsoft said that a patch addressing the flaw should be released on April 14
• However, most outdated Windows 7 systems will not receive such an update
• Meanwhile, the tech firm has released a list of workarounds for users to employ

https://www.dailymail.co.uk/sciencetech/article-8146679/Microsoft-says-hackers-exploiting-vulnerability-versions-Windows.html

Hackers are attacking recent versions of Windows, dating back to Windows 7 and Windows Server 2008 R2.  The hackers are able to exploit a bug in the font rendering engine, which allows for them to take control of the machine.  Currently, there is no fix or protection against this vulnerability other than NOT OPENING UNKNOWN DOCUMENTS.  This applies to previews of the document as well. 

This also affects PDF documents.

This is a serious issues, and Microsoft expects to have a patch available by April 14th.