common.php

/*...*/ 
$usr['ip'] = ($cfg['clustermode']) ? $_SERVER['HTTP_X_CLUSTER_CLIENT_IP'] : $_SERVER['REMOTE_ADDR'] ; 
/*...*/ 

$userip = explode('.', $usr['ip']); 

fix

$usr['ip'] = ($cfg['clustermode']) ? $_SERVER['HTTP_X_CLUSTER_CLIENT_IP'] : $_SERVER['REMOTE_ADDR'] ; 
if (!preg_match('#^\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}$#', $usr['ip'])) { $usr['ip'] = '0.0.0.0'; }