Strava — a fitness app that links to smartphones and wearable fitness trackers to collect information about exercise habits — released a data visualization map of users' activity, which could reveal the location of secret U.S. military bases, the Guardian reports.

Why it matters: This is a significant security threat because it makes U.S. bases not only identifiable, but mappable to anyone who has access to this fitness app.

The information of military personnel who use Strava was also shared on the heat map, leaving the outposts susceptible to detection.

“In Syria, known coalition (i.e. U.S.) bases light up the night. Some light markers [are] over known Russian positions," writes Middle East institude analyst Tobias Schneider.