These were driving me nuts too, but here is how you can fix it (at least it's working for me so far). Make the Windows Firewall work for you - block all inbound / outbound communication from ccleaner.exe and ccleaner64.exe
Open up a run box - key in wf.msc
Go to Inbound rules - right-click New Rule. Rule for Program - Click Next (%systemdrive%\Program Files\CCleaner\ccleaner.exe) - Block the Connection - Leave All Set - Give it a name Block CCleaner - hit Finish.
Then, make another rule for "%systemdrive%\Program Files\CCleaner\ccleaner64.exe" - same settings.
Finally - make both the same rules under Outbound Rules as well.
While you're at it - go under Task Scheduler, delete the CCleaner Update task.
You could also run these commands to create the firewall rules at the Command Line:
netsh advfirewall firewall add rule name="CCleaner Block" dir=in action=block program="C:\Program Files\CCleaner\ccleaner.exe" enable=yes
netsh advfirewall firewall add rule name="CCleaner64 Block" dir=in action=block program="C:\Program Files\CCleaner\ccleaner64.exe" enable=yes
netsh advfirewall firewall add rule name="CCleaner Block" dir=out action=block program="C:\Program Files\CCleaner\ccleaner.exe" enable=yes
netsh advfirewall firewall add rule name="CCleaner64 Block" dir=out action=block program="C:\Program Files\CCleaner\ccleaner64.exe" enable=yes
Also, be sure to uncheck "Help improve CCleaner by sending anonymous usage data". Disable Smart Cleaning, remove "Inform me of updates". You can also go ahead and change the Cookie settings to delete all cookies again (even Avast, etc...).
Even after disabling automatic updates, send usage statistics, and smart cleaning - I still got the following traffic blocked right after opening. My guess is this is where they are hosting the ads. CCleaner should not need internet access.
151.101.186.109 51495 443 0 - 0 0 0 - - - SEND
5.62.44.206 51496 443 0 - 0 0 0 - - - SEND
5.62.48.202 51497 443 0 - 0 0 0 - - - SEND
5.62.48.54 51498 443 0 - 0 0 0 - - - SEND
5.62.44.204 51499 443 0 - 0 0 0 - - - SEND
5.62.44.205 51500 443 0 - 0 0 0 - - - SEND
I've been using CCleaner forever, but these new versions are really getting on my nerves. It might be time for me to find another cleaner to recommend for everyone I do computer work for.