Personal Information Leakage During Password Recovery of Internet   Services
  In this paper we examine the standard password recovery process of large Internet services such as Gmail, Facebook, and Twitter. Although most of these services try to maintain user privacy, with regard to registration information and other personal information provided by the user, we demonstrate that personal information can still be obtained by unauthorized individuals or attackers. This information includes the full (or partial) email address, phone number, friends list, address, etc. We examine different scenarios and demonstrate how the details revealed in the password recovery process can be used to deduct more focused information about users. 
Mordechai Guri, Eyal Shemer, Dov Shirtz, Yuval Elovici
cs.CR