Software Engineering Institute

According to Apple:

WebKit is the open source core of Apple's Safari web browser. It is available as a framework in Mac OS X for use in your applications.
More information about WebKit is available at the WebKit Project web site.

The Apple Webkit fails to properly perform type conversions when rendering frame sets possibly allowing memory corruption to occur. If a remote attacker persuades a user to access a specially crafted web page with software that uses WebKit, that attacker may be able corrupt memory in a way that will let them execute arbitrary code.

This vulnerability may affect any software that uses the Apple WebKit, including the Safari web browser.

Note that this vulnerability is reported to affect software on both the Windows and Apple OS X operating systems.

A remote, unauthenticated attacker may be able to execute arbitrary code.

Apply Apple Updates
Apple has released an update to address this vulnerability. Refer to Apple Security Update 2007-006 for more information.

According to Apple:
Safari 3 Beta Update 3.0.2 will appear for systems running Safari 3 Beta and includes the entire contents of Security Update 2007-006. Security Update 2007-006 itself will not appear via Software Update for systems that have installed Safari 3 Beta.