Microsoft is now detecting CCleaner Windows optimization and Registry cleaner program as a potentially unwanted application (PUA) in Microsoft Defender. Microsoft has stated that they do not support Registry cleaners and that they should not be used. Microsoft’s evaluation criteria state that displaying “misleading”” or “”inaccurate”” claims about files and registry entries would cause a program to fall under the classification of a. potentially unwanted program. Microsoft told BleepingComputer that this detection is only targeting the free version as it includes bundled “”offers”” for other software.”
Source: https://www.bleepingcomputer.com/news/microsoft/microsoft-now-detects-ccleaner-as-a-potentially-unwanted-application/