An issue was discovered in libraries/common.inc.php in phpMyAdmin 4.0 before 4.0.10.20, 4.4.x, 4.6.x, and 4.7.0 prereleases. The restrictions caused by $cfg[\'Servers\'][$i][\'AllowNoPassword\'] = false are bypassed under certain PHP versions (e.g., version 5). This can allow the login of users who have no password set even if the administrator has set $cfg[\'Servers\'][$i][\'AllowNoPassword\'] to false (which is also the default). This occurs because some implementations of the PHP substr function return false when given \'\' as the first argument.