PCVARK is a major developer of Mac PUPs (potentially unwanted programs) PCVark is responsible for gems like Advanced Mac Cleaner and Mac Adware Cleaner. Mac File Opener is an app that can open most files that are at all likely to be on the typical users system. If there is no other app to open a specific file, this app would be the default. It turns out that this is exactly what that app wants, and it takes full advantage of that fact.”]
Source: https://blog.malwarebytes.com/threat-analysis/2016/08/pcvark-plays-dirty/