Automatic updated

Hi there,
I want to ask this.

I had several mails coming in saying that

Howdy! Your site at http://blablabla has been updated automatically to WordPress 3.7.2.

For more on version 3.7.2, see the About WordPress screen:
(see site)

WordPress 3.8.2 is also now available. Updating is easy and only takes a few moments:

Keeping your site updated is important for security. It also makes the internet a safer place for you and your readers.

If you experience any issues or need support, the volunteers in the ww.wp.xz.cn support forums may be able to help.
ww.wp.xz.cn/support/

The WordPress Team

Is this normal? Since it’s the first time it happened to me.
It didn’t happen to all the sites I manage, just a few.
Several sites, different versions