The location of a number of secret military bases has been revealed in maps created by the fitness tracking app, Strava.
In what's being described as a major security oversight, the highly sensitive information appears to reveal the detailed layout of army outposts and troop movements.
Millions of people in the US and Europe use Strava to track their whereabouts while exercising, either on a smartphone or other devise.
But the app's maps also pinpoint users in war zones such as Afghanistan and Syria. Those users are believed to be almost uniquely American or from other western military.
Experts admit the disclosure is a serious lapse in security, though doubt it will put lives at risk.
Ewan Lawson from The Royal United Services Institute said: "Well, I think it's serious, but perhaps lives are not anymore at risk than perhaps they were yesterday. This will be more information, confirmatory information perhaps, but images of these sort of locations are available on commercial satellite imagery and those that have an interest in where these locations are will have had a pretty idea before, what Strava does is simply add to that picture."
The Pentagon has said it is examining the Strava heatmaps to access their implications for its security.