Update on the security hole: John Gruber of Daring Fireball has a nice clear post about how to disable unsafe URI handlers using an application which, for reasons he explains well, is better suited to this situation than MisFox or MoreInternet -- RCDefaultApp.

(By the way, for the curious, Simon Willison has posted a sample AppleScript snippet showing how distressingly simple this exploit is. Also, if you're interested, read Peter da Silva's sage comment on the architectural reasons this hole exists.)

So where's that fix from Apple, anyway?