There is a rising concern among parents who have experienced unreliable content maturity ratings for mobile applications (apps) that result in inappropriate risk exposure for their children and adolescents. In reality, there is no consistent maturity rating policy for mobile applications. The maturity ratings of Android apps are provided purely by developers' self-disclosure and are rarely verified. While Apple's iOS app ratings are considered to be more accurate, they can also be inconsistent with Apple's published policies. To address these issues, this research aims to systematically uncover the extent and severity of unreliable maturity ratings for mobile apps. Specifically, we develop mechanisms to verify the maturity ratings of mobile apps and investigate possible reasons behind the incorrect ratings. We believe that our findings have important implications for platform providers (e.g., Google or Apple) as well as for regulatory bodies and application developers. Copyright is held by the International World Wide Web Conference Committee (IW3C2).