The question that came to your mind is " How Is It Possible?" imagine your phone battery status spying on you this time its not a spy keyboard or a virus, if this is true, Ad-blocker or VPN cant stop it.
Allow me to explain, an unpleasant application is responsible for this, it tracks all you do online and its very hard to control.
A paper published by Security Researchers from Princeton University, explain how this attack occur, the paper says it takes advantage of the HTML5 Baterry Status Application Programming Interface(API). The code is present in Google Chrome, Firefox and Opera Browsers, the function of this code present in those device was to allow site owners view the battery level of visiting device so as to enable them serve a low-power version of the site to the device if the device battery is low.
Two of the researchers, Steve Engelhard and Arvind Narayanan with the aid of a modified browser discovered two tracking scripts that make use of the API to “fingerprint” a certain device. This in turn allows software to differentiate and recognize each devices.
A group of privacy researchers warned about the potential threats about a year ago, stating that it could be used to spy on users, and it is finally becoming a reality. One of the researchers, Lukasz Olejnik in a recent blog post stressed that some companies may exploit customers by using the battery level indicator. As a matter of fact, Uber made an announcement in May, claiming that users are willing to pay a higher price when their device is running low on power.
Browser owners are beginning to explore this feature and contemplating if they will disable this feature or not. For now this solution is charging your device when the battery is low.