class Rack::Protection::FrameOptions

to allow embedding from the same origin (default).
frame. Use :deny to forbid any embedding, :sameorigin
frame_options
Defines who should be allowed to embed the page in a
Options:
in a frame.
Sets X-Frame-Options header to tell the browser avoid embedding the page
More infos
developer.mozilla.org/en/The_X-FRAME-OPTIONS_response_header<br>Safari 4.0, Chrome 4.1.249.1042 and later
Supported browsers
Internet Explorer 8, Firefox 3.6.9, Opera 10.50,
Prevented attack

Clickjacking
#

def call(env) 

def call(env)
  status, headers, body        = @app.call(env)
  headers['X-Frame-Options'] ||= frame_options if html? headers
  [status, headers, body]
end

def frame_options 

def frame_options
  @frame_options ||= begin
    frame_options = options[:frame_options]
    frame_options = options[:frame_options].to_s.upcase unless frame_options.respond_to? :to_str
    frame_options.to_str
  end
end