Bitdefender just removed this ccleaner trojan!

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Published Sep 20, 2017|Updated Sep 20, 2017

Backdoor:Win32/Floxif.gen!A

Alert level: Severe Detected with Windows Defender Antivirus

Also detected as: No associated aliases

Windows Defender Antivirus detects and removes this threat.

The threat is a backdoor trojan that is related to the "trojanized" version of a third-party utility known as "CCleaner".

as you saying this happened with the latest v5.42.6499 release or are you running the old, infected version of CC?

You either have an outdated ccleaner or still had an old installer laying around because it's catching the september 2017 version of ccleaner which was indeed infected.