Strava is a mobile fitness tracking app that uses GPS data from phones and watches. It has access to a lot of data, and has been using that data to create a global heat map showing the paths taken by its cycling and running customers. The map’s most recent update, last November, aggregates user data through September 2017. But analyst Nathan Ruser noticed a problem: in places where local Strava use is low, the map can reveal the paths of people from wealthy western countries—for example, soldiers at U.S. military bases overseas, whether they’re patrolling or simply exercising. (U.S. troops are encouraged to use fitness trackers.) Which is to say, suddenly Strava is a security problem. Details at BBC News and the Washington Post.