Wow. Around ten days after I have reported on the screen saver vulnerability here, the bug finally made into forums that are more closely watched by Apple than my blog. Quickly afterwards, Apple released a security update. Fine.
I wonder if this bug was totally new to Apple as the news was already hopping around the scene for a while and I considered it to be public knowledge somehow. But obviously I was wrong or Apple didn‘t care.
Something else I would consider to be part of public knowledge is the current state of preference management on OS X. Many people have already experienced what happens when your disk gets full: many Apple branded applications seem to „forget“ their preferences: Mail, iTunes and the Finder are the most prominent. It is totally unclear to me how this can happen at all. Seems to be a major programming snafu in my opinion.
Let me review what is usually happening. First your disk gets full – usually anything less than 100 MB free space can be considered really dangerous. If Mail.app is running it more or less immediately empties its preference file (~/Library/Preferences/com.apple.mail.plist) completely: when you look at the file it contains zero bytes. And this happens even if you are not changing anything in your preferences.
I don‘t say your mail is gone: it is still residing in ~/Library/Mail. But without the information in its preference file, Mail no longer knows about your accounts and with it goes the information on where to find the mail storage. When you restart the application all the messages seem to be gone.
Recovery is difficult unless you have a fresh copy of your preference file. You can retype your account settings but your mail rules are totally fucked up: all the target folder information is lost. In my case this means clicking on around 100 rules setting the target folder. This is more than annoying.
Here is my workaround: when you notice that your disk is full do NOT quit any running applications. Instead, make room on your disk by moving/deleting some files and then open ANY preference dialog you can get your hands on. While the preferences are held in memory you need to reopen them with your application and click „Save“ to make sure the correct settings are written to the file. Do this with Mail and the Finder (don‘t forget the „Customize Toolbar“ command) and hopefully you are safe.
To be really safe, I recommend making a regular backup of your whole Preferences folder so that you can manually copy back all lost settings.
So now I am waiting for the next public outcry. I would hope that the whole issue is resolved with Panther but it would be an insult if there won‘t be a free fix for Jaguar pretty soon.