Target Fragmentation in Android Apps

Android apps declare a target version of the Android run-time platform. When run on devices with more recent Android versions, apps are executed in a compatibility mode that attempts to mimic the behavior of the older target version. This design has serious security consequences. Apps that target outdated Android versions disable important security changes to the Android platform. We call the problem of apps targeting outdated Android versions the target fragmentation problem. We analyze a dataset of 1,232,696 free Android apps collected between May, 2012 and December, 2015 and show that the target fragmentation problem is a serious concern across the entire app ecosystem and has not changed considerably in several years. In total, 93% of current apps target out-of-date platform versions and have a mean outdatedness of 686 days, 79% of apps are already out-of-date on the day they are uploaded to the app store. Finally, we examine seven security related changes to the Android platform that are disabled in apps that target outdated platform versions and show that target fragmentation hamstrings attempts to improve the security of Android apps.