For the purposes of tailoring the Android to different hardware platforms, countries/regions and other needs, hardware manufacturers (e.g. Qualcomm), device manufacturers, carriers and others have aggressively customized Android into thousands of system images. This practice has led to a highly fragmented ecosystem where the complicated relations among its components and apps though which one party interacts with the other have been seriously compromised. This leads to the pervasiveness of Hare (hanging attribute references e.g. package, activity, service action names, authorities and permissions), a type of vulnerabilities never investigated before. In this talk, we will show that such flaws could have serious security implications, that is, a malicious app can acquire critical system capabilities by pretending to be the owner of an attribute who has been used on a device while the party defining it does not exist due to vendor customizations. On the factory image of 97 most popular Android devices, we discovered 21557 likely Hare flaws, demonstrating the significant impacts of the problem from stealing user's voice notes, controlling the screen unlock process, replacing Google Email's account settings to injecting messages into Facebook app and Skype. We will also show a set of new techniques we developed for automatically detecting Hare flaws within different Android versions, which can be utilized by the device manufacturers and other parties to secure their custom OSes. And we will provide the guidance for avoiding this pitfall when building future systems.