The Paktor app allows you to find out email addresses, and not just of those users that are viewed.All you need to do is intercept the traffic, which is easy enough to do on your own device.This allows an attacker, for example, to see which accounts the victim is currently viewing.
The Mamba dating service stands apart from all the other apps.
In Happn for Android there is an additional search option: among the data about the users being viewed that the server sends to the application, there is the parameter fb_id – a specially generated identification number for the Facebook account.
The app uses it to find out how many friends the user has in common on Facebook.
Most of the apps in our research are vulnerable when it comes to identifying user locations prior to an attack, although this threat has already been mentioned in several studies (for instance, here and here).
We found that users of Tinder, Mamba, Zoosk, Happn, We Chat, and Paktor are particularly susceptible to this.