We don't recommend using WP at all. We never have, and never will. It's notorious for crap like this, and has one of the worst track records for CMS security...just about any other program out there is more secure than the steaming pile that is WP. The hack in question does seem to affect the latest version though, as several people (both here and other places online) reported that fully updated, no-extension installs were compromised by AnonymousFox. Last I heard, WP is denying an issue exists though it quite obviously does based on the numerous reports across the web.