Ask almost any security expert, and they'll tell you switching on "unknown sources" on your Android phone or tablet is one of the worst things you can do for device security.
But that's exactly what Amazon has asked its app store customers to do for years.
The heart of the problem is Amazon's requirement to allow installations from "unknown sources" -- that is, any app or game that hasn't been carefully vetted by the Google Play app store. That's because while almost all of Amazon's apps are already in Google Play, the retail giant's own third-party app store, dubbed Underground, isn't allowed.
Opening your Android phone or tablet up to apps and games outside Google's protective walled garden also makes your device infinitely more vulnerable to malware.
A spokesperson for Amazon said "millions" of devices have Underground installed, but warned that "customers should take care only to download content from sources they trust, like Amazon." That includes Amazon Prime Video -- the company's competitor to Netflix -- which is only available on Android through the Amazon Underground store.
But it's not Amazon's app store that's the problem -- it's the giant hole you have to punch in Android's security to get it installed in the first place.
You can read more of this story on our sister site ZDNet.