Amazon was sued on Wednesday by consumers who accused the retailing giant of secretly tracking their movements through their cellphones, and selling data it collects.

According to a proposed class action in San Francisco federal court, Amazon obtained “backdoor access” to consumers’ phones by providing tens of thousands of app developers with code known as Amazon Ads SDK to be embedded in their apps.

This allegedly enabled Amazon to collect an enormous amount of timestamped geolocation data about where consumers live, work, shop and visit, revealing sensitive information such as religious affiliations, sexual orientations and health concerns.