I usually used Ccleaner for cleaning junk & liked its ease of editing the start menu.
However just today I was installing it on a friends computer and whilst reading info in the middle of the install screen/template and going through with the install I noticed to the far left it had a check box to install Avast. Unfortunately because my attention was drawn to the center of the screen I did not notice this until right after allowing it to proceed & could not stop it nor could I uninstall Avast afterward.
It is a bad idea to have an AV install auto checked because most people already have one installed & this can cause conflicts.
Plus it should be unchecked and allow a user to install it if they read it and opt to use it.
I advise not to set it up as checked and to not trick people into installing it or anything else ever again.
As far as I am concerned the developers for this application stooped very low in doing that.
I will no longer use CCleaner nor will I advise anyone else to use it.
In fact I will now advise them against using it or anything else developed by Piriform.
It's been pre-selected like this ever since they started offering Avast. (They had started doing the same before that when they used to offer Chrome or the Google toolbar).
Many people have complained about it, many have had unwanted installs of Avast (or Chrome) because of it.
But Piriform have done nothing and obviously don't want to change it.
(There have also been problems with the Avast install happening even when the offer was never even shown. I've had that one twice myself).
Either be very careful when installing or updating CCleaner, or block connections to Avast in your firewall.