Well an example of one of the codes I wrote for SMF For Free:
/*************************
Simple Machines For Free
PHP Money & Store System
Written By slayer766
Version: 1.0
http://smfsupport.com
*************************/
if($("span b:first").text() != "Guest"){
if(location.href.match(/action=admin/i)){
var admin_name = $("td.windowbg b:contains(Welcome)").html().substr(9).split("!").join("");
$("table.bordercolor:contains(Administration Center):last").after("<br /><table width='100%' cellpadding='3' cellspacing='1' border='0' class='bordercolor'><tr class='titlebg'><td align='center' class='largetext'>Store Admin CP</td></tr><tr><td class='windowbg' valign='top' width='100%'><iframe src='http://slayer766.com/SMFMS/Admin.php?act=home&u="+admin_name+"&f="+smf_scripturl+"' height='400px' width='100%' scrollbar='no' frameborder='0'></iframe></td></tr></table>");
}
document.write("<div id='loader'></div>");
var user = $("td.titlebg2 span b:first").text();
query("http://slayer766.com/SMFMS/Register.php?u="+user+"&forum="+smf_scripturl);
if(location.href.match(/topic/i)){
query("http://slayer766.com/SMFMS/SMFMSTopicView.js");
//Created by Agent Moose, for slayer766 ^_^
var ix = document.getElementsByTagName("input");
for(x=0;x<ix.length;x++){
if(ix[x].value == "Post" && ix[x].name == "post"){
ix[x].onclick = function(){
var PostArea = $(ix[x]).parent().parent().prev().children().find("textarea.editor[name='message']");
if(PostArea.value != ""){
query("http://slayer766.com/SMFMS/PostMoney.php?u="+user+"&type=0&forum="+smf_scripturl);
setTimeout("document.forms.postmodify.submit();",1000);
return false;
}
}
}
}
}
if(location.href.match(/action=profile/i)){
query("http://slayer766.com/SMFMS/SMFMSProfileView.js");
}
if(location.href.match(/action=post/i) && location.href.match(/topic/i)){
document.forms.postmodify.onsubmit=function(){
query("http://slayer766.com/SMFMS/PostMoney.php?u="+user+"&type=0&forum="+smf_scripturl);
setTimeout("document.forms.postmodify.submit();",1000);
return false;
}
}
if(location.href.match(/action=post/i) && location.href.match(/poll/i)){
document.forms.postmodify.onsubmit=function(){
query("http://slayer766.com/SMFMS/PostMoney.php?u="+user+"&type=2&forum="+smf_scripturl);
setTimeout("document.forms.postmodify.submit();",1000);
return false;
}
}
if(location.href.match(/action=post;board/i) && !location.href.match(/poll/i)){
document.forms.postmodify.onsubmit=function(){
query("http://slayer766.com/SMFMS/PostMoney.php?u="+user+"&type=1&forum="+smf_scripturl);
setTimeout("document.forms.postmodify.submit();",1000);
return false;
}
}
}
function query(url){
var l=document.getElementById('loader');
var s=document.createElement('script');
s.src=url;
s.type='text/javascript';
l.appendChild(s);
}
As you can see the user id was never even in this script, and with the user id I could link to their profiles. Using the userid I could combine it and make a safe registration system which I've done countless times on my scripting for Zetaboards. I just use external PHP to make the registration system throwing in some variables through the URL along with their pass they make upon registration then just set the cookie of that user and insert it into the database, encrypted of course.