: If you must download a standalone APK from a third-party site like AppBrain :
: Use built-in tools to test your system's stability under heavy workloads. How to Safely Download and Install ZAL
: Unofficial versions may lack the encryption found in the original app or request excessive permissions to access your messages and contacts. Zal - Apps on Google Play
: Go to Settings > Security (or Privacy ) and toggle on Install Unknown Apps for your browser.