WordPress 4.3 brings with it the introduction of the site icons API, which gives the ability for site owners to define their own favicon within the dashboard, without the assistance of a plugin or hard coding into the site template.
This new functionality is available straight out of the box with no need to implement any scripts; via the theme customizer, users can now upload and define their very own site icon. Not only will this icon be automatically pulled into a site browser bar, it will also appear within the site dashboard where in the past no icon would appear, giving a nice consistent feel throughout.
Checkout full details of what was released in WordPress 4.3.