How many clicks does it take?
blog.jgc.org
blog.jgc.org
In any case, I doubt the author tried this out. All multiple signon does is allow you to easily switched between accounts which you are logged in. Logging out of one doesn't affect the others, and changing the password of one doesn't change the password of any other account. It's basically a glorified switcher, and there's no vulnerability to speak of. I know this because I pseudo-linked the accounts, cleared all cookies and logged back in, and I was only linked in one account versus the three I had before.
It would be good if people reporting vulnerabilities actually tested them first :/
I remember cases here in Germany, where big companies were spying on their employees, so the scenario of the "evil sysadmin" might even include the sysadmin who is being coaxed by his superiors.