iPhone 1.0.1 was released and is available through iTunes when the iPhone is connected. While the notes were not specific on what has been fixed, it was widely reported that security researchers were set to reveal details of a critical security flaw in the iPhone at the Black Hat 2007 conference this week. The update was expected to fix that flaw before the conference.
The notes provided with Safari beta 3.0.3 only say that the update improves security and stability. The update is available via the software update mechanism in Mac OS X.
Security Update 2007-007 1.0 improves the security for several components of the operating system including bzip2, CFNetwork, Core Audio, cscope, gnuzip, Kerberos, mDNSResponder, PDFKit, PHP, Quartz Composer, samba, WebKit and WebCore.