If I try to upgrade vtiger, I am getting an illegal request message, nothing happens, any Idea whats going wrong?
Check if $site_URL Variable is correct in config.inc.php file? also you can disable this error by editing the following file includes/http/Request.php
around line 207-207 on validateReferer function find
throw new Exception('Illegal request');
change to
//throw new Exception('Illegal request');