Android APK Checklist

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Learn Android fundamentals

• Basics
• Dalvik & Smali
• Entry points
  • Activities
  • URL Schemes
  • Content Providers
  • Services
  • Broadcast Receivers
  • Intents
  • Intent Filter
• Other components
• How to use ADB
• How to modify Smali

Static Analysis

• Check for the use of obfuscation, checks for noting if the mobile was rooted, if an emulator is being used and anti-tampering checks. Read this for more info.
• Sensitive applications (like bank apps) should check if the mobile is rooted and should actuate in consequence.
• Search for interesting strings (passwords, URLs, API, encryption, backdoors, tokens, Bluetooth uuids...).
  • Special attention to firebase APIs.
• Read the manifest:
  • Check if the application is in debug mode and try to "exploit" it
  • Check if the APK allows backups
  • Exported Activities
  • Content Providers
  • Exposed services
  • Broadcast Receivers
  • URL Schemes
• Is the application saving data insecurely internally or externally?
• Is there any password hard coded or saved in disk? Is the app using insecurely crypto algorithms?
• All the libraries compiled using the PIE flag?
• Don't forget that there is a bunch of static Android Analyzers that can help you a lot during this phase.

Dynamic Analysis

• Prepare the environment (online, local VM or physical)
• Is there any unintended data leakage (logging, copy/paste, crash logs)?
• Confidential information being saved in SQLite dbs?
• Exploitable exposed Activities?
• Exploitable Content Providers?
• Exploitable exposed Services?
• Exploitable Broadcast Receivers?
• Is the application transmitting information in clear text/using weak algorithms? is a MitM possible?
• Inspect HTTP/HTTPS traffic
  • This one is really important, because if you can capture the HTTP traffic you can search for common Web vulnerabilities (Hacktricks has a lot of information about Web vulns).
• Check for possible Android Client Side Injections (probably some static code analysis will help here)
• Frida: Just Frida, use it to obtain interesting dynamic data from the application (maybe some passwords...)

Some obfuscation/Deobfuscation information

• Read here