Suppose I am logged in to Stack Exchange on Firefox on my work computer. This session is clearly stored as a cookie (or something else), because it persists when I reboot the computer. I have sudo access on my computer, but so does the network administrator. This means that they have access to all files on the computer and can use
su to log in as me. Let us consider only remote login (as I can easily log out of every site before giving physical access if needed).
I guess it is possible for a remote sudo user to use my Stack Exchange cookie to impersonate me on Stack Exchange. But maybe the browser (Firefox) or the server (Stack Exchange) have some security mechanisms that make this harder. How easy would it be for a sudo user to login remotely and use my Stack Exchange cookie to impersonate me on Stack Exchange? Would the answer be different if I were using a different browser or logged in to a different server (such as Google, Yahoo, etc)?