yum-firefoxwarn is a plugin for Yum which deals with the situation where Mozilla Firefox is running while it is being upgraded to a newer version, making the running instance behave unpredictably and eventually crashing. This is a problem in larger-scale environments where users don't control the yum updates and they have long-lived Firefox sessions.
Firefox instability due to silent upgrades creates frustrated users which in turn increases pressure on the support organisations. This plugin will warn users in this situation so that they can restart Firefox in a controlled manner.
The warning makes use of a zenity process running externally to yum, so yum will not hang while waiting for the user to acknowledge.