Military personnel around the world have been publicly sharing their exercise routes online – including those inside or near military bases.
Online fitness tracker Strava has published a “heatmap” showing the paths its users log as they run or cycle.
It appears to show the structure of foreign military bases in countries like Syria and Afghanistan, as soldiers move around inside.
The US military is examining the heatmap, a spokesman said.
Air Force Colonel John Thomas, a spokesman for US Central Command, told the Washington Post that the US military was reviewing the implications.
Strava said it had excluded activities marked as private from the map.
Users who record their exercise data on Strava have the option of making their movements public or private. Private data, the company said, has never been included.
The appearance of military bases on the heatmap suggests that large numbers of military personnel across the globe have been publicly sharing their location data.
The latest version of the map was released in November 2017, but the implications for service personnel were only raised over the weekend.