There appears to be a single system-wide clipboard which is globally readable and writable; this represents a huge security hole.
A user can not only read anything which any other user places on the clipboard, they can replace it with content of their choosing. Even if no one is behaving in a malicious manner, this keeps multiple users from functionally using a clipboard at the same time.
(By way of demonstration, install xcopy and xpaste, and open up shells as two different users, root or otherwise. Copy as one user, paste as the other... same content.)