The current build is here:
XTension Version 9.4.20
The builds on this page are historical and not currently supported.
XTension releases come on a weekly release schedule rather than on an official numbering scheme. You can get the latest build from the XTension Version 9.4.20 page. By downloading this software you agree to be bound by the end user license agreement.
(IMPORTANT NOTE: if you’re upgrading from a version prior to build 854 then you must run 854 at least once against the database to convert your applescripts into a format readable by Cocoa. After the database conversion is complete you can then run versions 855 or newer)