Before trusting any trading app we should investigate about the app that is officially published or not. Because we can find sometime many 3rd party trading app on the play store and  app store which is not officially launched. So if you choose some of them you can be hacked or lost your money. And always need to aware about new trading app even exchanges.

Anyway personally I trust Binance , Kucoin and coinbene trading app which I have used before. And worked smoothly without any security issues.