
1)You have to be authenticated
2)You have to be able to pass it a command
So yeah, its a vulnerabilty for people who open themselves to SQL injection attacks already. Well whoopee. I would assume anyone open to SQL Injection is running its webservers with close to sysadmin rights anyway, and xp_cmdshell enabled.
So the excitement is fairly limited, as they say.
The real lesson from this advisory is if you are fairly tight on security anyway, a simple escalation of rights on this proc should see you right.
Bit of a non story, shouldn't have got past the ms advisories.