Getting multiple "updated to 3.8.4" emails

I am receiving multiple messages from my site saying that it has been updated to 3.8.4 automatically.

I have seen that automatic updates were introduced in 3.7 already.

When I look at my dashboard, I see that it says that it is using 3.8.4-alpha.

When I try to display the about.php file, it says that the site is in maintenance mode – and then a few minutes later, displays correctly !

Is this a bug ?
Should I turn off automatic updates for the present ?