To fix the problem manually locate the tpl_searchform() function in inc/template.php and replace the following line (around 495):
print 'value="'.$_REQUEST['id'].'" '; /* keep search input as long as user stays on search page */
with this line:
print 'value="'.htmlspecialchars($_REQUEST['id']).'" '; /* keep search input as long as user stays on search page */
The available archive of release 2005-09-22 at
http://splitbrain.org/go/dokuwiki was updated accordingly