It has been reported that the built-in antivirus in the Windows 10 software platform, Windows Defender (Microsoft Defender), now classifies the CCleaner application as potentially unwanted. This follows information that was recently posted on the official Microsoft Security Intelligence page.

As a reminder, the CCleaner application is a utility designed to clean and optimize the operating system by removing unnecessary files, cleaning the registry, and more. In the past, developers have stated that Microsoft does not support registry cleaning programs and does not recommend their use.
"Some software products, such as registry cleaning utilities, suggest that the registry needs regular maintenance or cleaning. However, incorrect modifications to the registry using these utilities can lead to serious problems. These problems may require a reinstallation of the operating system. Microsoft cannot guarantee that issues potentially caused by such utilities can be resolved without reinstalling the system," stated Microsoft in a message published previously.
Microsoft believes that software should not mislead users by displaying messages with inaccurate or exaggerated information about the state of the operating system, registry entries, and other elements. The company explained that at this time, the status of potentially unwanted application will only be assigned to the free version of CCleaner, as it prompts users to install additional software that is not required for the utility to function. This primarily concerns other products from Piriform, the developer of CCleaner.
A representative from Piriform stated that the company considers the addition of the utility to the potentially unwanted list as a "false positive." Currently, CCleaner developers are discussing possible solutions to this issue with Microsoft and hope that the situation will change soon.
Source:
Source: 3dnews.ru
