I tried to update debian (my first time) and Apper quickly warned me that I was about to install unsigned packages and that it was impossible to verify if they came from a trusted source: Do you want to continue? I decided to take a risk and clicked 'yes'. This led to another warning window requiring me to reenter my password. At this point I bottled out and cancelled the update.
I would have thought that only trusted software would be put into the updates so was surprised by this and would like to ask for a bit of explanation and also advice on how to proceed.