Just got my update a short time ago, have you gotten yours. Looks like Firefox 18.104.22.168.4 was released yesterday afternoon, and if you have automatic updates enabled in Firefox, you should be getting it yourself in 24-48 hours. This looks to be like a critical security update because only one change mentioned in the release notes. Wasn’t rolled in together with any other fixes.
Here are the details from Mozilla:
To update you can activate your automatic updates, go to help and then “check for updates” or download the most recent version at getfirefox.com.