I just ran across what I consider a security hole in Font Book. When you double-click a font in the OS X Finder (one that has not yet been installed), Font Book launches and shows a sample of the selected font. The sample window also includes a button which allows the user to install the font. The Font Book default for installing a new font is to install it system-wide in the top-level Library -> Fonts folder (as opposed to your user's Library -> Fonts folder). Furthermore, no admin password is required of a non-admin user to install a new font. This opens up the door for users to easily install corrupt fonts (or replace system fonts with a corrupt file) that could wreak havoc on the OS for all users.
To change the default behavior, simply go to the preferences in Font Book and select the option that says install new fonts "for me only." Unfortunately, the current user can easily change this option prior to installing a font. IMO, Apple should make this option changeable only by an admin user.
[robg adds: On three machines I looked at, two of which had never run Font Book before, the install option was already set to "for me only." So the hint in this hint may not be necessary on your machine. The more interesting question to me is how big of a security hole is this? What can be hidden in a font file? Other than making life difficult by installing a corrupted font, are worse things possible? And since the 'attacker' will already have physical access and a login account, it seems there are much worse things that he/she could do in this case. Thoughts?]
Mac OS X Hints
http://hints.macworld.com/article.php?story=20041102020349669