The newest version of PHP was just released, which addresses several vulnerabilities:
http://www.securityfocus.com/bid/29009
http://www.securityfocus.com/bid/27786
Any code written in PHP is potentially affected by this, depending on which functions you use, so don't forget to update!
What functions specifically? :)
Dunno, read. :P
Apparently there's an overflow in one of the regexp libraries, that's the only one I noticed.