This was simply a matter of Phoenix (or their web hosting service) not renewing their security certificate (key). Without that key, your browser can't be sure the site is who they say they are. That key costs money since the root certificate holder provides a service.
It is only used on secure (https://) URLs but pretty much all sites now only provide https connections.
The fact that your browser gave you the warning means YOUR web browser Is secure and doing its job.
No anti-virus or Anti-Malware programs is needed to get the warning. CCleaner, is not needed to provide the warning.
I am not saying don't use CCleaner, that's up to each individual. I am just saying it does nothing for this particular issue.