The owner of AFF, Nichiren, recently posted about this. I'm copying his message here for those of you not friends with him:

Some people have told me about an AFF app on the Play store. I took a look and it looks like they put a wrapper around our mobile site and packaged it into an app which is an easy thing to do. So here's the thing: I don't know who they are. If you use it, you're giving your credentials to a third party and risking your private data since they could have packaged the app with other code that do other things. What worries me is that I've looked at the reviews and there are too many people that think it's an official Asianfanfics app and I have no idea what it could be doing to your data behind the scenes if you install it and log in. If something bad were to happen, people would think that Asianfanfics is responsible so that is definitely a concern to me.

Rest assured, I'm working on getting a proper AFF app published. If you don't know about the app fundraiser, check it out on our app fundraising page and be eligible for the app founder badge. The app will be natively built for performance, have push notifications, and you won't need an internet connection to read stories. An app like that takes time and we need to raise enough from the fundraiser to get it to where it needs to be.

Just be careful installing anything that claims to be from us. I haven't published any official apps yet so it would pretty easy to tell. I don't have a wide reach on this account so let your friends know too.

Nath note: I saw this from a friend and I think is better to let more to know, continue to pass this ahead ^^