Fitness app Strava announced it is reviewing certain features on their app, after it was revealed on Sunday that the fitness app released information including the location of some covert American military bases since the app had been used while military personnel were exercising and been shared with others.

Strava disclosed a map with every activity ever uploaded to the app in November 2017. As a result, the public could view runs military personnel have taken on secret bases.

Strava CEO John Quarles said in an open letter Monday the "heatmap" was intended to provide a “visualization of activities around the world” and was designed to help users find areas to be active.

“In building it, we respected activity and profile privacy selections, including the ability to opt out of heatmaps altogether,” Quarles said in the letter. “However, we learned over the weekend that Strava members in the military, humanitarian workers and others living abroad may have shared their location in areas without other activity density and, in doing so, inadvertently increased awareness of sensitive locations.”

“Many team members at Strava and in our community, including me, have family members in the armed forces,” Quarles wrote. “Please know that we are taking this matter seriously and understand our responsibility related to the data you share with us.”

Strava said the organization is working with the military and other government officials to tackle information that could be sensitive and that it is reevaluating certain features. Additionally, the company said it would work on simplifying privacy and safety features and continue to boost awareness regarding privacy and safety tools so users are more conscious about how control what they share.

The map released showed bases in Afghanistan, Djibouti, Syria, and other countries.

The app tracks the location of those using fitness gear like Fitbits that record where a user goes during runs, walks, or bike rides.