As you all know, even if WhatsApp is for mobile phones, we can access and existing WhatsApp account using the web version. In the beginning, the service was available if your mobile and the desktop is in the same network, but now can be available anywhere on any device using the link http://web.whatsapp.com.
This feature was very useful mainly for those who are using laptop or desktop all the time. Even during the work, we can check and send messages from the browser itself. We don’t need to look into the mobile all the time. We are also able to receive notification within the browser. However, it is a good feature; there is some downside; also, most commonly, other people can monitor the account of one person.
In WhatsApp, we get maximum security so that there is less chance of your account being hacked. But here, the problem occurs knowingly or unknowingly. In some case, we may give our phones to other people of some other purpose, but here, what they can do is open a web version of WhatsApp on their mobile or desktop and can scan and log in your WhatsApp account on their mobile. So they can read and send your WhatsApp messages from their device until you logout the device from your WhatsApp account.
So, if you need to check your WhatsApp is being logged in at any other location, please go to WhatsApp settings, then select WhatsApp Web. If you see the screen below, it is okay. Your account is safe and not logged in at any other device. Its currently showing a scan window to start login. So it is fair, you are safe.
And if you see the screen like below, you can see the list of all the logged-in device. Please check the login time and device to confirm it is you or someone else. If you found anything suspicious, click on the Log out from all computers. You will ask for confirmation, click on Log Out.
Now your account will be logged out from all other devices, and you will see a screen like the first. So you are safe now.
Do check this regularly or if you find anything unusual. If you are accessing the web version from Internet Cafe or any public places, please remember to logout like this.