The CCleaner was judged as "potentially undesirable software" from Microsoft Defender, the built-in antivirus of Windows 10.

Microsoft Defender has identified the popular utility program as a potentially unwanted application, formerly Windows Defender renamed with information of May 2020.
Potentially unwanted software, more commonly referred to as "potentially unwanted applications" (or PUAs), refers to applications in which an antivirus does not find malicious content, but may display unwanted behavior, such as Windows-detected CCleaner.
Usually, this means merging extra tracks, or hidden installation add-ons such as a browser plug-in, which may not harm computer but it could prove to be annoying.
As identified by Bleeping Computer, Defender detected CCleaner as PUA, with the Windows developer stating that "theSome installations for free and 14-day trial versions of CCleaner come with built-in applications, including applications not required by CCleaner. "
"While grouped applications are legal, combining software, especially products from other providers, can lead to unexpected software activity that can adversely affect the user experience."
These grouped applications include Google Browser ChromeThe Google Toolbar and Avast Free Antivirus and AVG Antivirus Free Note that Piriform is now owned by Avast, which also has AVG.
Η Microsoft stressed that these grouped applications are completely secure and not at all malicious, of course, it is the way they are offered for installation that is problematic.
The company noted that while the CCleaner installation process provides a way to avoid installing these add-ons on your computer, the problem is thatSome users can easily inadvertently install these grouped applications».
According to a statement just was released CCleaner, the company believes that the issue pointed out by Windows has been resolved.

«We are in the process of working with Microsoft to understand why CCleaner was detected recently as PUA. We assume that the issue appears to be related to grouping and we believe that we have addressed it so that our product is no longer labeled by Windows,Said a CCleaner spokesman
Now, if you install CCleaner while running Microsoft Defender, it may not warn you of dangers, assuming that the security application has actually been updated.