hello shadownate, i think this is a normal process when you are a [http://windows.microsoft.com/en-US/windows-8/join-maps-community member of MAPS (Microsoft Active Protection Service)] and chose to submit information about unknown applications. in case microsoft defender comes across an application version that doesn't show up in ms' database yet (which might well be the case for firefox executables immediately after an update), they upload the file and analyse it - this is the way they gather new information to create signatures for unknown threats. Plugin-container.exe & maintenanceservice.exe are part of firefox and won't pose a risk to your system.