class Rack::Protection::ReferrerPolicy

referrer_policy
The policy to use (default: ‘strict-origin-when-cross-origin’)
Options:
Sets Referrer-Policy header to tell the browser to limit the Referer header.
More infos
www.w3.org/TR/referrer-policy/
Supported browsers
mixed support
Prevented attack

Secret leakage, third party tracking
#

def call(env) 

def call(env)
  status, headers, body = @app.call(env)
  headers['Referrer-Policy'] ||= options[:referrer_policy]
  [status, headers, body]
end