Chinese smartphones with Android OS contain backdoors in its firwmare - backdoors that are sending sending your personal information to Chinese servers.
Phone manufacturers in China equip those smartphones with tracking software that is used to send information to the local government and censors. Without the user knowingit, automatically and without an option to turn it of. We should add that the phones with this firmware came also to the US - how surprising ...
More:
http://thehackernews.com/2016/11/hacking-android-smartphone.html
http://www.kryptowire.com/adups_security_analysis.html