[Trusty] Software updater installs packages from proposed updates?

[cogset]

I've noticed that some updates from trusty-proposed were installed in ubuntu trusty a couple of days ago by the update manager, this one http://packages.ubuntu.com/trusty-updates/systemd and some other related packages.

The changelog says
systemd (204-5ubuntu20.20) trusty-proposed; urgency=medium
but I'm positive I don't have trusty-proposed in my sources neither I've checked proposed updates in the software manager: am I missing something here?

Why am I getting software from proposed updates ?

[deadflowr]

The proposed in the changelog means the package was originally uploaded there. persumably for further testing.
That was on Nov 10.
It has since been adequately tested and approved, so they moved it to trusty-updates.