Intent Redirection & Exported Components

Android apps message each other with Intents, and components marked "exported" are doors any app can knock on. The trouble starts when an exported component takes a caller-supplied Intent and blindly fires it back out, using the victim app's own identity and permissions. That is intent redirection: a confused deputy lending out access the attacker never had. How exported components work, how the bug arises, how to find and trigger it with adb and drozer, and how to shut it.