A paper published last year revealed that the battery on a laptop or phone can be used to track one's online activities. The vulnerability resided in a built-in HTML 5 specification, which could be tricked into identifying people and tracking their online activities. One year later, we are now learning that the vulnerability is being exploited in the wild. The Guardian reports: [...] Two security researchers from Princeton University have shown that the battery status indicator really is being used in the wild to track users. By running a specially modified browser, Steve Engelhard and Arvind Narayanan found two tracking scripts that used the API to "fingerprint" a specific device, allowing them to continuously identify it across multiple contexts. The research was highlighted by Lukasz Olejnik, one of the four researchers who first called attention to the potential issues with the battery status API in 2015. Although Olejnik achieved some success following his warning, with the body in charge of the web's standards thanking his group for the privacy analysis, the API still has the potential for misuse. And while it is only tracking scripts using it now, Olejnik warns that unscrupulous actors could do more. "Some companies may be analysing the possibility of monetising the access to battery levels," he writes. "When battery is running low, people might be prone to some -- otherwise different -- decisions. In such circumstances, users will agree to pay more for a service."