The APK Downloader, downloads original APKs from Google (Playstore) server,
this makes the probability of malware contamination practically 0%, but you should always scan these APKs with a virus (multi) scanner to minimize this possible risk. This Firefox add-on, is the best of its type, because it lets you:
1. the device type
2. the Android version
3. processor architectures
4. and much more!
Specifying, it lets you bypass countries and Android restrictions.
That is why this very good add-on gets a full 5 stars Rating! I am visibly excited!