Following my own advice, I use File History with Windows 10. I also keep Windows 10 Defender up to date. So I was a bit surprised, even alarmed, when I got the notification that a "Backdoor:Win32/Floxif" was found on my machine.
It was found in a file archived by File History. I run the 64bit version of CCleaner which was not compromised. I also update freeware promptly when notified by Filehippo. The exploit took place during the takeover of
Piriform by Avast. Details are obscure but Avast has issued a rather detailed explanation of the matter at https://blog.avast.com/progress-on-ccleaner-investigation
To paraphrase Mayor Daily "Update early and often!"