I don't think there has been such a quick release of Postnuke after the previous as now. Version .723 can now be downloaded at the Postnuke site. The why? Well, since .722 contained a big change to to core code, some security leaks were found and made the release a lot quicker to be released than expected.
So to all of you who have .722 running, upgrade your version to .723 to avoid getting hacked! I've upgraded my site here as soon as I heard about it.