This ESLint plugin provides rules to enforce safe usage of `_.extend()` and `$.extend()` functions, helping prevent accidental modification of source objects when developers intend to create new objects. It's designed for JavaScript developers using Underscore.js or jQuery who want to catch common mistakes where `extend()` is called without an initial empty object, which can lead to unintended side effects. The plugin is particularly useful for teams working on projects where `extend()` misuse could cause subtle bugs or data corruption.