Facebook paid people to download its Facebook Research App from the testing grounds. The app tracked participants’ phone and online activity. People who agreed to take part in the program were given a “clear on-boarding process asking for their permission,” according to a Facebook spokesperson. Teens and adults signed up and were paid by Facebook to participate in the program, which tracked users’ phone and online activity through Facebook’s market research app. The app was first reported by TechCrunch, which said users were paid up to in $20 a month in gift cards. Facebook distributed the iOS app, called Facebook Research, to consumers through Apple’s “Enterprise Developer Program.” This program allows companies such as Facebook to test and distribute apps for their own employees to use, not the general public or consumers. “Facebook has been using their membership to distribute a data-collecting app to consumers, which is a clear breach of their agreement with Apple,” an Apple spokesperson said. “Any developer using their enterprise certificates to distribute apps to consumers will have their certificates revoked, which is what we did in this case to protect our users and their data.” A Facebook spokesperson said Apple’s action also impacted the social network’s internal iOS apps that employees use. According to TechCrunch, Facebook’s research app may have been able to access information such as private messages, web searches and location data. Users who agreed to take part in the program were given a “clear on-boarding process asking for their permission,” according to a Facebook spokesperson. The spokesperson also told CNN Business that the app was not “spying” on people. “Key facts about this market research program are being ignored,” the spokesperson said. “There was nothing ‘secret’ about this; it was literally called the Facebook Research App.” The spokesperson added that less than 5% of participants were teens, and said that all of them signed parental consent forms. Facebook previously pulled similar iOS app called Onavo after Apple said the VPN tool violated its data-collection rules. That app is still available on Android. “It’s very clear to the people who participate in, it’s completely opt in, there’s a rigorous consent flow and people are compensated. It’s a market research program. Now, that said, we know we have work to do to make sure people’s data is protected. It’s your information,” Facebook COO Sheryl Sandberg said on CNBC. “As soon as we realized we weren’t in compliance with the rules on their platform we pulled it.” Facebook continues to deal with the fallout from privacy scandals and concerns about how it handles user data. Last year, political research firm Cambridge Analytica improperly harvested information on tens of millions of Facebook users. In October, Facebook said hackers accessed the phone numbers and email addresses of nearly 30 million users.