If you are using Redis Store (or any non-cookie storage) for your Rails sessions and you've got a nasty bug while using
domain: :all option (as described here: https://github.com/rails/rails/issues/2483).
There is a temporary fix for that:
gem 'gem 'cookie_jar_fix', git: 'git://gist.github.com/2958645.git'
NOTICE: As now, the fix has been accepted (https://github.com/rails/rails/pull/6084) but only in master (
git branch --contains 41219386 returns just 'master'), that's why this microgem strictly requires ActionPack 3.2.6.