Let's guess: A popup on Phn "It downloads as 4" kaskas.apx : kskas-2.apex
isn't produce any result googling: Apx is linkable to special download apps
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Some websites that have to do with android will try to get gullible users to install their adware/malware/spyware when certain pages are viewed. This especially applies to sites that host third-party sources for android app APKs. Be very careful, chances are that the APK is malicious... I once had an article about android 7 auto-download a "System monitor" APK that quite literally had every conceivable permission in it, including the ability to mount and unmount filesystems! There's some scary stuff out there.