No permission set on Activities [Android App]

How it was found

Android app version: 1.0.0

Issue Details:

The following activities are exported and it does not have a permission set.

1. com.owncloud.android.ui.activity.FileDisplayActivity
2. com.owncloud.android.ui.activity.ReceiveExternalFilesActivity
3. com.owncloud.android.authentication.AuthenticatorActivity
4. com.owncloud.android.ui.activity.ShareActivity

This could allow any malicious application to initiate the above mentioned activities thus bypassing security checks or getting private information of any user.

Recommendation:

Set the permission for the above mentioned activities or either set android:exported=false (which allows the activities to be launched by only components of the same app or the same uid)