5
In fact the solution is to modify the lines concerned in the findusers/main.php page according to the following presentation:
case XOOPS_MATCH_START:
$criteria->add(new Criteria('user_fieldx', $myts->addSlashes(trim($HTTP_POST_VARS['user_fieldx'])).'%', 'LIKE'));
break;
case XOOPS_MATCH_END:
$criteria->add(new Criteria('user_fieldx', '%'.$myts->addSlashes(trim($HTTP_POST_VARS['user_fieldx'])), 'LIKE'));
break;
case XOOPS_MATCH_EQUAL:
$criteria->add(new Criteria('user_fieldx', $myts->addSlashes(trim($HTTP_POST_VARS['user_fieldx']))));
break;
case XOOPS_MATCH_CONTAIN:
$criteria->add(new Criteria('user_fieldx', '%'.$myts->addSlashes(trim($HTTP_POST_VARS['user_fieldx'])).'%', 'LIKE'));
break;
(which was not previously the case)