I received this message when updating Operating System from the AppCenter. How could this update not be from a trusted source? Could it be that my AppCenter has been compromised?Dialog window in question

  • 1
    You probably added a ppa that's not secure so unless you are sure it's safe to update don't do it. Delete such PPA if you think it's not safe
    – Maccer
    Commented Nov 26, 2016 at 10:27
  • any news? I've the same problem..
    – Paolo Zaia
    Commented Dec 10, 2016 at 9:52
  • Maccer was right, I added the Arc GTK repo without adding the key. After importing the key, the error was fixed.
    Commented Dec 11, 2016 at 13:18
  • how can I add the key? I'm a bit new on Linux..
    – Paolo Zaia
    Commented Dec 16, 2016 at 8:31

1 Answer 1


There is a repository key missing. To fix this, you can add the key in a terminal window with the following command:

wget --quiet http://download.opensuse.org/repositories/home:Horst3180/xUbuntu_16.04/Release.key -O - | sudo apt-key add -

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