The CCleaner software tool was recently infected with Malware. This is a very popular and legitimate tool used by many professionals and laypersons alike.
If you used CCleaner between 8/15/17 and 9/11/17, you should uninstall it and then download and install the latest version which has been fixed. Also, make sure to run some security scans with your antivirus software to make sure your computer system is clean.
Please see this link for further details:
Please let us know if you have any questions, or need any help with this.