Vulnerabilità script AJAX

[starcraftworld]

Ho scritto questo script in AJAX:

function update (object, container) {
    if (object.length>0) {
        var url="./script/update.php?page="+object;
        XMLHTTP=switchBrowser(function () { setContent(container) });
        XMLHTTP.open("GET",url,true);
        XMLHTTP.send(null);
    }
    else {
        document.getElementById(container).innerHTML = "";
    }
}

function setContent (container) {
    if (XMLHTTP.readyState==4) {
        var element=document.getElementById(container);
        element.innerHTML=XMLHTTP.responseText;
    }
}

function switchBrowser (browser) {
    if (navigator.userAgent.indexOf("MSIE")!=(-1)) {
        var cat="Msxml2.XMLHTTP";
        if (navigator.appVersion.indexOf("MSIE 5.5")!=(-1)) {
            cat="Microsoft.XMLHTTP";
        }
        try {
            objectXMLHTTP=new ActiveXObject(cat);
            objectXMLHTTP.onreadystatechange=browser;
            return objectXMLHTTP;
        }
        catch(e) {
            alert("Errore");
        }
    }
    else {
        objectXMLHTTP=new XMLHttpRequest();
        objectXMLHTTP.onload=browser;
        objectXMLHTTP.onerror=browser;
        return objectXMLHTTP;
    }
}

update.php

 
<?php
    $page=$_GET['page'];
    include("../".$page);
?>

Questo script comporta qualche vulnerabilità o problemi di sicurezza?