While our smartphones have definitely become more capable and smarter, the phone functionality itself has remained locked in the 20th century. There have been many attempts to make the phone app itself even smarter. Google's dialer app is one. Third-party TrueCaller, which is making its way to the likes of Cyanogen OS and BLU Products devices, is another. Yet for all the convenience that the service might bring, one single design flaw potentially exposed the private details of 100 million Android users who have downloaded the app in good faith.