This release fixes a recently declared XSS vulnerability. Anyone using Tikiwiki 1.9.x should upgrade as soon as possible. This release only fixes the security flaw and doesn't include any new feature.
This vulnerability is fixed by setting up proper var checks in tiki-setup_base.php. The 18.104.22.168 release includes an updated version of that file, so you can secure your own tiki by just replacing that file with the current tiki-setup_base.php from cvs.
Note that the only other fix included in that release is about the italian language file that was broken in 22.214.171.124.