title: Security of services or receiver with exported true and without intent filters in Android
body: <p>Concerning Android security: </p>
  
  <ol>
  <li>Can a service or receiver with exported=true and without intent filter create an open door for other applications to send explicit intents which are not manageable by the receiver?</li>
  <li>Is there an Android feature beyond permissions to protect against this situation?</li>
  <li>How can a receiver protect itself when use of this mechanism is really necessary?</li>
  </ol>