WhatsApp doesnt properly erase your deleted messages, researcher reveals. The flaw could be exploited by attackers to snoop on users private conversations, even when they gave been deleted The only way to get rid of them appears to be to delete the app entirely. The issue represents a serious problem for users that live in an oppressive country, there is the concrete risk that authorities access sensitive conversations by physically accessing the mobile device. Other applications that suffer a similar problem, including Apple iMessageas explained by Jonathan Zdziarski.”]
Source: http://securityaffairs.co/wordpress/49892/mobile-2/whatsapp-deleted-messages.html