Codeigniter (CSRF) jQuery ajax problem

check value of your $config['csrf_token_name'] in /application/config/config.php as default is setted as csrf_test_name not csrf_token_name.

This decision if you not want to use PHP code in Javascript.

$.ajax({
    url: 'some_url',
    type: 'POST',
    data: {csrf_test_name: $.cookie('csrf_cookie_name')}
});

This code works fine.

Try (javascript):

var ID = $(".imageWrap:last").attr("id");
var baseurl = "http://localhost/woho/";
var doScroll = 1;
var cct = $.cookie("<?php echo $this->config->item("csrf_cookie_name"); ?>");

if (location.href == baseurl) {
    $(window).scroll(function(){
        if ($(window).scrollTop() > $('body').height() / 2) {
            if(doScroll == 1) {                   
                $.post(baseurl + 'ajax/images',{'id':ID,'<?php echo $this->security->get_csrf_token_name(); ?>': cct}, function(data) {
                    alert(data);
                    $("#wrapper_content").append(data);
                    ID++;
                });
            }
        }
    });
}