And a solution for first bug (XSS):

File: functions.php, function redirect()

FIND:
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function redirect($url, $message="", $title="")
{
global $header, $footer, $mybb, $theme, $headerinclude, $templates, $lang, $plugins;

$redirect_args = array(?url? => &$url, ?message? => &$message, ?title? => &$title);

$plugins->run_hooks_by_ref(?redirect?, $redirect_args);

if($mybb->input['ajax'])
----------------
REPLACE WITH:
----------------
function redirect($url, $message="", $title="")
{
global $header, $footer, $mybb, $theme, $headerinclude, $templates, $lang, $plugins;

$redirect_args = array(?url? => &$url, ?message? => &$message, ?title? => &$title);

$plugins->run_hooks_by_ref(?redirect?, $redirect_args);

$url = addslashes($url) ;
if($mybb->input['ajax'])
----------------

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