Apps collecting data on their users is nothing new, but some have taken it too far.

Popular travel apps, such as Air Canada, Hollister, and Expedia, are secretly recording iPhone users’ screens, according to a TechCrunch report.  The practice, commonly known as session replaying, allows app developers to record screens in order to see how users are interacting with the app. In this case, TechCrunch reported developers used a third-party firm, the case analytics firm Glassbox, to embed the technology into their mobile apps.

After learning of developer’s actions, Apple is telling developers to disclose screen recordings to users or remove the code responsible, according to a new TechCrunch report.  Apple confirmed that its App Store Review Guidelines do not allow session replaying without gaining consent from users first.

“Protecting user privacy is paramount in the Apple ecosystem. Our App Store Review Guidelines require that apps request explicit user consent and provide a clear visual indication when recording, logging, or otherwise making a record of user activity,” an Apple spokesperson told TechCrunch.

The spokesperson went on to say developers have been informed they are in violation of “these strict privacy terms” and the company will “take immediate action if necessary.”

Some apps using the technology were also failing to mask sensitive user data, as reported by The Verge. The outlet noted Air Canada was not properly masking screen replay files when sent to company servers, leaving them open interception.

Although the current case of secret recordings is limited to iPhone users, TechCrunch reported Glassbox is also available to all Android app developers.

Apple has given developers less than a day to remove the code and resubmit the app or have their app removed from the app store.