This is not much more of a vulnerability than the current possibility of having a telnet connection hijacked on an unsecured outside machine. The primary additional risk comes from people being able to use the term socket you set up without you even being aware of it. So be careful out there. (Personally, I do this with an outside machine I know to be pretty secure, namely a linux laptop I maintain myself that does not accept any incoming connections.)
Another possibility is to add "socket off" to the remote
~/.term/termrc.telnet, or
add "-u off" to invocation of term.
This prevents the socket from being hijacked from the remote end,
with only a minor loss of functionality.