If your leak is at the spigot then as long as there's liquid in there pushing against the leak, there is constant positive pressure on the inside of the bucket in that location- it's gonna be a one-way street leading out, not in. No worries about contamination, just losing beer.
You can't be a real country unless you have a beer and an airline. It helps if you have some kind of a football team, or some nuclear weapons, but at the very least you need a beer. -Frank Zappa