BBF:
It is better and easier to do this instead:
The template edit you already did:
Find in credits_manage template
HTML Code:
<if condition="$show['donate']">
<form action="credits.php?do=donate" method="post">
<input type="hidden" name="s" value="$session[sessionhash]" />
add below
HTML Code:
<input type="hidden" name="securitytoken" value="$bbuserinfo[securitytoken]" />
remove those file edits to credits.php, and instead find
PHP Code:
define('THIS_SCRIPT', 'credits');
add below
PHP Code:
define('CSRF_PROTECTION', true);
and now the security token stuff will be handled by vbulletin automatically