There is a chance when downloading the latest version of CCleaner that your anti-virus program will flag the installer for CCleaner to contain a Trojan, and/or a Virus.
This is a what we call a "false positive". Meaning that there is actually not a virus inside the program. It's usually caused by the Google bundle that is inside the setup file. The issue is usually fixed within 24 hours.
There are a few things you can do to fix the problem too. If you receive a Trojan/Virus warning when trying to install CCleaner, please report this "false positive" to the company in which makes the anti-virus program you use. You can also wait a few days until the Slim build is released (it doesn't contain the Google bundle).
Thank you for using CCleaner!