"Joker" is a relatively new form of malware that reportedly acts to steal contacts and sign those with infected devices up for premium SMS services. Most recently, it has been detected in a heretofore-overlooked host on Android by the Pradeo security team. This lab has had the app removed from the Google Play Store, but potentially affected users are advised to uninstall it immediately.
https://www.notebookcheck.net/The-Joker-malware-is-found-to-exist-within-yet-another-Android-app.440208.0.html