At the moment there are hardcoded strings for shortname (MantisBT search) and description (MantisBT Text Search) of the browser search plugin (see browser_search_plugin.php)
So if you browse more than one instance of MantisBT you are not able to distinguish them.

This should be replaced by a configuration option combined with a localized string.
$g_window_title or $g_page_title could be used for this, or if makes more sense a new option $g_search_title

Something like:
$search_title = config_get( 'window_title' ) . ' - ' . lang_get( 'search' );
$search_description = config_get( 'window_title' ) . ' - ' . lang_get( 'text_search' );

There is also a hardcoded icon included which could be replaced by $g_favicon_image or maybe a new option is needed.