The latest update has some sneaky nastiness added for some. When you are installing you need to make sure the tiny little box on the bottom left hand side of the screen (make ccleaner your default browser or some such) is not ticked. Please note it is quite small and has never been there before so I missed it. I thought I just needed to change the default browser back and all would be fine. Until I discovered all of my pdf files were now ccleaner files. Grrrrrr. The easiest solution is to just u
The CCleaner Browser is only being offered to a limited number of users when Updating CCleaner itself.
Most browsers will change your file associations when you first install them.
If/when this happens then it's easy enough to change them back.
For the example of PDF files:
Right click on any PDF file and select 'Open With > ' and then 'Choose another app'.
Choose the application that you want to open PDFs with, then tick "Always use this App to open PDF files'.