The PHP development team have suggested that everyone immediately upgrade to PHP 4.3.10 due to a number of very serious flaws in previous versions that can result in your server being “owned”.
Expect most Linux distro’s to release patched versions of PHP in the coming days. If your using a Windows server you’ll have to dig up an updated version yourself, using Windows, you’ve already put yourself at a security disadvantage, so you really should make this a priority.
Franki