One of my sites automatically upgraded to 3.9.1 earlier this evening, then a couple of hours later I got an email saying it had automatically upgraded to an alpha version WordPress 4.0-alpha-20140507.
On the wordpress updates page in admin it says: BETA TESTERS: This site is set up to install updates of future beta versions automatically. I'm pretty sure I never set this, though I won't rule out myself making a mistake. Is it possible that there was a bug that caused this?
I can't find anywhere that controls what updates should apply, though I don't recall setting it up to install beta and alpha versions. From searching I found something called a beta tester plugin, though I don't have any such plugin installed on my sites.
I'm a bit lost at this point as to what is going on, where I would turn automatic updates off or check the settings etc. I'm happy enough with finalised updates being automatic but I'd rather not be installing beta and alpha versions.