We have a Sakai that accepts this parameter:
So, when you enter with this skin into Sakai, from this moment in all the sites without a defined skin you will see the skin in the parameter. If a site has a skin selected you will see the selected skin.
We use this to allow different enterprises to use the same Sakai. They must access to Sakai from a link in their webpage and that link has the parameter. If someone enters without the parameter we have a very simple default skin without logos.
The patch affects the KERNEL, the PORTAL and the LOGIN TOOL (this third one because we allow the same parameter when callin directly the xlogin page)