Apple still hasn't fixed a Safari bug that's been known about for 2 years
pcworld.idg.com.au
pcworld.idg.com.au
I don't think this kind of a attack is that practical on OS X as there's no way of automatically executing a downloaded executable (as far as I know) and OS X's sandbox would kick in with a dialog confirming that the file should be opened on the off-chance the user did elect to open something random from the internet.
It's arguable that this could be a more powerful attack by taking advantage of an exploit in the handling of one of the "Safe" formats that are (by default) opened automatically (Movies, Pictures, etc). However, such an attack would be more subtle if it were just used inline in a webpage which makes the issue a bit redundant.
Case-in-point: Mozilla bug #350 https://bugzilla.mozilla.org/show_bug.cgi?id=350 was open for 11 years: that means it predates Netscape Navigator 4.06, but it wasn't fixed until Firefox 3.