It seems like the App Store has been neglected - updates don't seem to come here https://itunes.apple.com/gb/app/ccleaner/id499268461?mt=12
CCleaner doesn't comply with Apple's sandbox requirements (it's able to delete other files in the file system) and, as a result; new versions are not permitted to be uploaded there.
Just a question for the developers, can't you edit the Information block at the top (of the Mac App Store) telling people they should visit piriform.com for the latest version? Or does Apple not allow to update information on rejected apps?