All my documents have changed to 'CDYUUQG' files, and contain gibberish

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[This is not an answer, but I see no other way to continue this thread without writing in this space. Like so much of libreoffice, this is a muddle.]

Thank you for your response.

Malfunction of Windows Defender? Not a clue, and no, I hadn't searched any Microsoft forums yet, hoping it would be a simple fix and hoping to avoid a many hours long search for futility, as so many computer 'help' forums are. I also wrote here since the only items on my pc affected were every single libreoffice document.

What size is the renamed document? I don't know to what you are referring, since, as I said in my original question, all of my libreoffice documents on my computer suddenly changed to this strange "ODT.CDYUUQG" suffix after the original files' names. The documents range from very small to moderately large. Most are simple text documents of a few pages or less.

Since reading your suggestion I have attempted to "cut the added extension (including the dot)", but simply renaming the file(s) does nothing, as they remain the mysterious "CDYUUQG" type of files.

I am running Windows 8, with LibreOffice 4.3.5.2.