Manual:$wgUseAjax

auto-suggestion for the search bar has to be enabled explicitly since 1.8.0, see $wgAjaxSearch

Security
"$wgUseAjax = true" was a security Issue in 1.6.x up to 1.9.0:

An XSS injection vulnerability was located in the AJAX support module, affecting MediaWiki 1.6.x and up when the optional setting $wgUseAjax is enabled.

There is no danger in the default configuration, with $wgUseAjax off.

If you are using an extension based on the optional Ajax module, either disable it or upgrade to a version containing the fix:


 * 1.9: fixed in 1.9.0rc2
 * 1.8: fixed in 1.8.3
 * 1.7: fixed in 1.7.2
 * 1.6: fixed in 1.6.9