Macbook with Filevault just logged itself in on restart?!

[filmbuff]

I've got a 2012 Macbook Air 13" with Filevault 2 set on it. I only have one account, my personal account with admin privileges and a very strong password. Something really weird just happened. Actually, it happened once or twice before but I thought I imagined it.

I hit restart to free up some space on my SSD and left for a few minutes. When I came back the screen was black. I pushed the power button, nothing. Then I unplugged it, waited a minute, and pressed the power button again. This time the computer booted and I got a normal startup sound. It booted up but instead of the login screen it went straight to loading the desktop! As normal for filevault I had a grey loading bar for a few seconds while it decrypted, then my desktop came up normally without me ever entering my password.

As you can imagine it's kind of disturbing that my machine could be shutdown with the SSD in a decrypted state for anyone to grab and have full access. Is this a known bug? I tried searching but just got tons of results relating to automatic login.

Edit: Sierra

 

[ApfelKuchen]

This description doesn't add up. There are various, conflicting circumstances. If it is indeed true, then you have found some sort of bug - if you can duplicate it, you should report it to Apple.

However, considering the design of FileVault and other aspects of the operating system, it's more likely that part of your description is in error (we're all fallible humans).

If FileVault is enabled, and the computer restarted, you must enter the password - the system cannot de-crypt without the password.

Automatic Login is disabled if you have FileVault enabled. So if Automatic Login seems to be enabled (check System Preferences > Users & Groups > Login Options), have you confirmed that FileVault is actually enabled (System Preferences > Security & Privacy > FileVault)?

In Sierra, all boot-ups show a loading bar, whether FileVault is enabled, or not. A loading bar prior to the login screen simply indicates a standard, unencrypted OS boot. If you have a login screen followed by a loading bar, that's proof of FileVault.

If you really restarted (rather than shutdown or put the machine to sleep), then it shouldn't have been on a black screen when you returned. That could be a sign of an abnormal shutdown, or maybe you chose a different option from the Apple menu.

If it was an abnormal shutdown, then you may have needed to hold the power button for 2-10 seconds to restart. If it was asleep, it should have awakened promptly after a keypress.

If it had shutdown, a startup sound and progress bar would have been normal. If it had been asleep, you wouldn't encounter a startup sound or progress bar.

If it was asleep, a password might or might not have been required, depending on System Preferences > Security & Privacy > General > Require password (duration) after sleep or screen saver begins.

Unless the battery was dead, unplugging the power for a minute does very little. It would trigger a change to some Energy Saver settings. Also, the MagSafe power adapter has an internal reset mechanism that responds to a disconnect (from the wall) of a minute or so, but a misbehaving power adapter isn't likely to affect login settings (it would affect startup difficulties).

So long as the MacBook Air has sufficient battery power, unplugging the power does not affect the boot condition of the computer - it effectively behaves as if it has an UPS. If it was booted or asleep before disconnecting, it would remain booted or asleep while disconnected.