Steps to reproduce:

1. Clone the repo git clone https://github.com/barttenbrinke/cancancan_issue.git
2. Run bundle install
3. Run rails db:migrate
4. Open http://localhost:3000/working_documents_controller/new
5. You should get a CanCan::AccessDenied exception, as cancancan checks can?(:new, Document) and you are not allowed in.
6. Open http://localhost:3000/broken_documents_controller/new
7. You should get a CanCan::AccessDenied exception, however cancancan just checks can?(:read, Document) and you are allowed to continue.

The Working Documents controller has:

class WorkingDocumentsController < ApplicationController
  authorize_resource class: Document

The Broken Documents controller has:

class BrokenDocumentsController < ApplicationController
  authorize_resource :document

Ability has:

class Ability
  include CanCan::Ability

  def initialize(session)
    can :read, Document
  end
end

I believe this is a bug and a security issue.