WhatsApp allows users to add a random phone number to their WhatsApp contact list. WhatsApp will show the profile picture of a user who is selling a used TV. This information can be used to make a targeted attack. Hackers can then impersonate an old friend in order to build a credible message. The malicious link will trigger a drive-by that will infect his mobile phone. The final stage is to send him a WhatsApp message containing a link referencing a relevant news for him. The message will be coming from a trusted source.”]
Source: http://securityaffairs.co/wordpress/26789/security/whatsapp-profile-picture-risky-feature.html