WhatsSpy Public is a web-based tool that could allow an attacker to access Whatsapp user information related to his activity. Maikel Zweerink has released the tool on GitLab as a proof-of-concept that WhatsApp privacy is broken. The tool is able to display user information in a friendly dashboard that includes events being displayed in a timeline. It also allows experts to compare timelines of two users in order to conduct cross analysis. It is possible to discover the exact moment when users start to use WhatsApp and when they disconnect from service.”]
Source: https://securityaffairs.co/wordpress/33299/hacking/whatsspy-public-spy-whatsapp-users.html