The key here is to pay attention to what repos you have 
installed/enabled.  I believe the yum-conf-sl6x is installed by default. 
  This repo will automatically keep you on the latest release of SL6. 
So yes, you were automatically upgraded to 6.6.

The decision to make 6x the default happened in 5.11 and 6.4.
http://www.scientificlinux.org/documentation/faq/faq-releases/#update-latest-release

I hope that clears it up for those who were blindsided.

-Mark

--
Mr. Mark V. Stodola
Senior Control Systems Engineer

National Electrostatics Corp.
P.O. Box 620310
Middleton, WI 53562-0310 USA
Phone: (608) 831-7600
Fax: (608) 831-9591

On 11/13/2014 01:40 AM, Dalibor Toman wrote:
> HI,
>
> I have found that this release (6.6) is somehow special and it is only a
> 'servicepack' containing all the updates.
>
> Thanks
>