If you have Malwarebytes Premium installed on your computer you may encounter an error when updating to the latest version of CCleaner. This is generally caused by the Ransomware Protection module in Malwarebytes Premium.
If you are unable to update to the latest version, you can temporarily disable the Ransomware Protection module in Malwarebytes Premium. This is done by going to Settings > Protection > Real-Time Protection > Ransomware Protection and toggling it off. The CCleaner update should then be able to complete successfully.
If you have already tried to update which has resulted in the loss of access to CCleaner you can download and install CCleaner Professional from here: