Timehop, a service targeted toward resurfacing old posts and photos on users’ social media accounts disclosed on Saturday that a security breach has led to the compromise of 21 million user data.

According to the company, authorized administrative user’s credentials were used by an unauthorized user to log into their Cloud Computing Provider On December 19, 2017. The unauthorized user created a new administrative user account, and began conducting reconnaissance activities within the company’s Cloud Computing Environment.

For the next two days, and on one day in March, 2018, and one day in June, 2018, the unauthorized user logged in again and continued to conduct reconnaissance, the company stated. On July 4, 2018, the criminals conducted activities including an attack against the production database, and transfer of data, which triggered an alarm that alerted the company’s engineers, causing them to investigate and implement security measures.

Some of the company’s security decisions led to a disruption in the access to Dropbox and Google Photos by users, since access keys were deactivated to stop the hackers from gaining access to personal photos.

Timehop stated that they are communicating with local and federal law enforcement officials and information security professionals to help them gauge the impact of the incident on their users.