Ok, we're working on a 6.5.3 as I type this. The fix is fairly quick, it only requires 2 files to be changed. Anyone running a version between 6.4 and 6.5.2 will want to apply this:
At the top of addpost.php you'll see this:
require ("./includes/main.inc.php");
right before that, add this:
define('ADDPOST',1);
Then, in addpost_newpoll.php, at the top, you'll see this:
// ------------------------------------
// THIS FILE IS INCLUDED BY ADDPOST.PHP
Right after that, add this:
if (!defined('ADDPOST')) {
exit;
}