http://jqueryui.com/download/ says 1.10 is stable and 1.9 is legacy, MediaWiki seems to have 1.8! I spent a while figuring out why some parts of jquery.ui.position were not working, until I checked out the version.
Version: 1.22.0
Severity: normal
See Also:
https://bugzilla.wikimedia.org/show_bug.cgi?id=44740