What does the message mean: WhatsApp is open on another computer or in another browser?

Question

Information Security

From time to time, usually after the computer goes to sleep (in the morning or after a long period of inactivity), the message

"Whatsapp is open on another computer or in another browser. Click =Use here= to use WhatsApp Web in this window" appears.
Whatsapp hack or not to worry?

iPhone + Mac

Answer 1

Hey! Such a message can most often pop up if someone else other than you has access to your Whatsapp, and this person has opened Whatsapp on his computer. As everyone knows, Whatsapp cannot be opened at the same time on different computers. If you opened it, then the other person will have the same window with the notification "the application is open on another computer."
You can also go into all sessions on your phone and see if Whatsapp is open on your own in another tab.

Answer 2

Open in the settings "WhatsApp Web" - you will see all the sessions.

More or less like this

Answer 3

And so I understood.
Attack vectors:
1) periodic access to a mobile phone with knowledge of the PIN code or a Trojan on the mobile phone. you need to intercept the SMS.
2) Trojan on mac os you can steal the token and hardware data to replace the hardware with the hacker's PC.
3) the tabs are doubled due to the extension of which
I suppose that since we are talking about a colleague, then you have a security guard / admin (colleague) at work who, through the installed DLP system on a working mac os, can monitor your traffic, and during system downtime enters in the OS and rummaging in vatsap, hence the activity while the computer is locked or otherwise connected to your session remotely.
Enable two-step verification for reliability, disable sms texts on the lock screen.
Give more introductory, whose mac os.