Itis possible for a maliciously crafted website to "carpet bomb" the Windows desktop or the Mac OS X Download destination folder with files according to Nitesh Dhanjani in his OiReilly blog. Apple is aware of the issue.
The reason this can happen is because Safari canit be configured to block the download of every resource a website offers up. While this isnit strictly a vulnerability, it could be an annoyance or worse since Leopard users wouldnit see the effect right away.
Mr. Dhanjani reported that he raised the issue with the Apple security team who responded that itis not an issue they want to tackle at this time.
The issue is really related to the design of HTML and how some browsers work. Right now, itis probably not a huge concern, but history has proven that any time something like this gets put on the back burner, someone will try to figure out a way to exploit it.
In the meantime, the best course is always to be mindful of where one is surfing. A possible strategy is, when itis necessary to surf in unknown territory, to do it in a VM created by Parallels Desktop or VMware fusion and checkpoint the VM. If something goes wrong, one can always revert to the checkpoint or blow out the VM client completely, leaving Mac OS X unaffected. Firefox is the default browser in all current Linux distributions, a browser well known to most Mac users.