Adobe have been busy! They have released Version 11.0.2 which plugs some security holes in Photoshop CS4. The security issues look pretty obscure and unlikely but its a good idea to install it anyway.
Open Photoshop CS4 and select the menu item: Help:Updates and follow instructions from there.
Photoshop CS5 in not affected by this bug.
You can read more about the issues here:
http://www.adobe.com/support/security/bulletins/apsb10-13.html