Sonim XP7700 User Manual page 35

Protecting Your Phone from Harmful Applications
Some applications can harm your device. It is
recommended to verify apps in order to help prevent
harmful software from being installed on your device To
prevent installation of application from unknown sources,
disable the option Unknown sources.
If you want to install applications from unknown sources,
enable Verify apps under Settings > Security, to verify if
the application is safe for installation.
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