How can I fix the error "CCleaner.app can't be opened because Apple cannot check it for malicious software"?

Recent versions of MacOS can have a problem with software that has not been bought from the App Store and may produce the following message when you try to open it:

Sample error message: CCleaner.app can't be opened because Apple cannot check it for malicious software.
  This software needs to be updated. Contact the developer for more information

"CCleaner.app can't be opened because Apple cannot check it for malicious software. This software needs to be updated. Contact the developer for more information"

This message is due to changes to the 'Gatekeeper' function of macOS made in the 10.15 'Catalina' update.

You can find out more about these changes at the following link: https://appleinsider.com/articles/19/06/03/apples-macos-catalina-is-first-to-require-app-notarization-by-default

If this message appears when you try to open your download of CCleaner for Mac, you can solve this problem by doing the following:

  1. Click "Show in Finder"
  2. Hold down the Control key on the keyboard and click CCleaner > click Open
  3. Click "Open Anyways"

Additionally, and if applicable, creating an exception for CCleaner in Catalina will ensure you won’t have any issues on your device.

  1. Click on the Apple logo from the Menu Bar (top-right corner of screen)
  2. Click System Preferences... > Security & Privacy
  3. At the bottom of the General tab, where it says "CCleaner.app was blocked from use because it is not from an identified developer" click "Open Anyway"
  4. Click "Open"

Afterwards, CCleaner will be saved as an exception in your security settings, and you should no longer experience any problems when attempting to open the app.