FYI there is a feature request to do that. The code has been developed and merged, but the applaince hasn't yet been rebuilt to include it. That will happen soon hopefully.

In the meantime, you may find the docs that were also developed regarding file permissions useful?! By default the appliance is currently locked down (as per best practice) but to support the upgrade plugin they need to be relaxed. So the next release will ship with relaxed permissions by default. But those docs will allow you to lock it down again if you wish.

Just in case it's not obvious, on the current appliance follow the last bit on that doc page (to loosen permissions), then you should be all good.