Some apps require access to make changes to system settings, but this is not security related access to the lock screen or passwords, but to change the ring tone or background, for example.
On the Oppo smartphones with ColorOS, these settings are somewhat hidden deep within the app permissions.
- Tap on Settings
- Tap on App management
- Tap on Special app access
- Tap on Modify system settings
- Choose an App
- Enable or disable Allow system setting modification