Microsoft Defender and Microsoft Edge on Windows 10 will automatically block potentially unwanted applications (PUAs) by default starting this month. Microsoft added a new ‘Potentially unwanted app blocking’ setting in Windows security that causes Microsoft Defender to block these types of applications. Microsoft has found over the years that programs marked as PUAs or PUPs should be classified as malware as they perform malicious behavior on a computer. Microsoft’s criteria for designating a program as a potentially unwanted application is listed below: Software that displays advertisements or promotions, or prompts you to complete surveys for other products or services in software other than itself.
Source: https://www.bleepingcomputer.com/news/microsoft/windows-10-to-automatically-block-potentially-unwanted-apps/