A Chrome browser extension developed by a Harvard College computer science student allows people to pinpoint and track the location of Facebook Messenger users.
The extension - called Marauders Map after the magical chart from the Harry Potter books that reveals the location of every person within Hogwarts School - works by scooping up the location data of Facebook Messenger users and plotting it on a map.
That Facebook has that data at its disposal is probably no surprise, but the ease with which it can be extracted from the social network, and the accuracy with which it can track someone - to within just one metre - may comes as a shock.
