ZXPInstaller is a simple cross-platform (OS X and Windows) installer for third-party Adobe extensions (.zxp files). It serves as a replacement for the Adobe Extension Manager, which has not been supported since CC 2014. It provides a drag-and-drop GUI for installation, and a website to which extension developers can point users to download the installer.
Updated on Dec 09 2019
Note: Although Finder indicates that this is version 0.25.3, the developer states that this is version 1.6.3.