A WhatsApp vulnerability could allow someone to find out who is talking to whom, according to software engineer Rob Heaton.
The issue is that your ‘online’ status can be queried by any of your contacts. If you go offline and then come back online to read and reply to a message, that fact can be logged. Correlating times when you come back online with times when other people do the same can allow patterns to be seen that effectively identify two people messaging each other.
The vulnerability can be exploited to spy on your sleeping patterns as well. This will allow anyone, who is a bit of tech savvy on the inside, to know precisely at what time you go to sleep and when you wake up. This is the most absurd part, anyone with a little curiosity and a laptop can abuse the flaw which is part of WhatsApp.
The same issue was found last year in Facebook Messenger, since the app also tells others when a user has been online, offline or idle. The flaw on Messenger also allows stalkers to graph when their friends are awake or asleep.