Labinator Quick Secure Updater

Labinator Quick Secure Updater (L-QSU) is a WordPress plugin that allows you to update your themes and plugins securely, easily, and quickly by supplying a zip file. Before any update, a backup copy of the chosen theme or plugin will be created and stored in your media folder.

UPDATE: As of WordPress 5.5, this feature is now included with your WordPress installation. As a result, this plugin is not required anymore.