Wow, Vienna scientists received the complete WhatsApp member directory, containing 3.5 billion user entries. Yes, it’s just the directory, no messages, but the whole directory was available online - totally unprotected.
Any more reasons for not using WhatsApp required

3.5 Billion Accounts: Complete WhatsApp Directory Retrieved and Evaluated
Vienna researchers retrieved all WhatsApp numbers. The 3.5 billion profiles represent the largest data leak in history—and it's worse than you might think.
www.heise.de · Security
Link author:
Daniel AJ Sokolov@newstik@social.heise.de