Firefox 21 Changed Plugins Folder

Today was the day to install patches for Firefox and the various plugins, and at first I couldn't get Firefox to see the plugins at all.  It turns out they moved the folder and it's not really well documented, and doesn't seem to be in the release notes.  Maybe publishing the fix will help someone.  Seems like this is going to really break things on distros if users upgrade.

Previously plugins on a multi-user server were in

[base_of_firefox]/firefox/plugins/

Now they are stored in

[base_of_firefox]/firefox/browser/plugins/