That high risk error, is part of the massive security fix Google did for the play store. Prior to it, malicious coders could take an app, rip out its insides, inject devious code to it, an repackage it, all while preserving the original signature. Which let them publish the app on the play store and all, under the same name and everything.
As you can imagine this is very dangerous, and could have happened to any app regardless. Rather than chastising it, you should praise it. Because when it shows up, that most likely means the app you are trying to download was detected and flagged as being malicious.
Currently none of the other app stores (including amazon) have this fix. And are therefore still extremely vulnerable. I advise that you only download apps from the play store, and never get them from outside sources.
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