```ruby
class ApplicationController < ActionController::Base
  # Prevent CSRF attacks by raising an exception.
  # For APIs, you may want to use :null_session instead.
  protect_from_forgery with: :exception
  rescue_from CanCan::AccessDenied do |exception|
    redirect_to root_url, alert: exception.message
  end
end
```

Clean up application controller script
user
```ruby
# Encoding: utf-8
# Application controller
class ApplicationController < ActionController::Base
  # Prevent CSRF attacks by raising an exception.
  # For APIs, you may want to use :null_session instead.
  protect_from_forgery with: :exception
  rescue_from CanCan::AccessDenied do |exception|
    redirect_to root_url, alert: exception.message
  end
end
```
assistant