Apple has mandated that starting April 28, 2026, all apps submitted to the App Store must be built with the latest iOS 26 SDK or later.  MABS 12.0 is the latest version that supports iOS 26.

If you're submitting an iOS app to the App Store, you must ensure that your mobile app package is generated using MABS 12.0  — otherwise your submission will be rejected by Apple. 

Steps to take before April 28

1. Check the MABS version configured for your app in your OutSystems environment.
2. Upgrade to the latest MABS version (12.0) that supports iOS 26.
3. Regenerate your app package and test before submitting to the App Store.

Apple announcement: https://developer.apple.com/news/?id=ueeok6yw