The security flaw is very simply executed. All it depends upon is for the user to open up a web page in the Apple Safari browser and it will crash the system. A specially crafted i-frame html code with an uncommonly large height is the code that does the breakage. It's available to see this in action
Carsten Eriam Secunia’s chief security technician had this to say
Based on our testing the impact could be more severe due to the type of crash and nature of the vulnerability i.e. crashing when giving it a try to write to invalid memory in a call to memmove(), Based on this we do consider remote code execution a possibility though it has not been proven at this time.”
Of course Microsoft have already been notified about this and are currently investigating the issue, hoping to patch any possible exploits before hackers reveal them.
This doesn’t look like to be an issue on any 32 bit versions of Windows, but it hasn’t been ruled out as a possibility on other x64 bit versions of Windows just as Vista and XP. But for now, there’s not a whole lot to worry about, just don’t go opening random web pages that person of influence emailed you in Safari.