What is ‘Bulli Bai’ controversy that has sparked outrage across nation?

Photos of hundreds of Muslim women were uploaded on an app called 'Bulli Bai', following which many took to social media to complain to the police. Taking to Twitter, a journalist, who is one of the women named in the app, claimed that a group called 'Bulli Bai' was created like 'Sulli Deals' on GitHub, which would collect photos of Muslim women from their social media accounts and encourage people to participate in their "auction".