Official Description: Library for legacy multi-dex support

CommonsWare’s Notes

This artifact provides MultiDexApplication, which allows you to use an insecure form of multidex on Android 4.4 and older devices.

Multidex allows your APK to contain multiple DEX files, each containing compiled Dalvik bytecode from your Java/Kotlin source. An individual DEX file is limited to 64K method references; having multiple DEX files allows your app to exceed this limit.

Multidex is native to Android 5.0 and higher. This quasi-backport of the capability makes it possible to exceed the 64K DEX method reference limit on Android 4.4 and below. However, this raises security problems: if something is able to attack your app’s portion of internal storage and replace one or more of your DEX files, the attacker can cause your app to run whatever the attacker wants. This sort of dynamic code loading is banned by the Play Store; it is merely a matter of time before the use of MultiDexApplication will itself be banned.