The Korn shell (aka mksh) before R33d on MirOS (aka MirBSD) does not flush the tty's I/O when invoking mksh in a new terminal, which allows local users to gain privileges by opening a virtual terminal and entering command sequences, which might later be executed in opportunistic circumstances by a different user who launches mksh and specifies that terminal with the -T option.
https://exchange.xforce.ibmcloud.com/vulnerabilities/41794
http://www.securityfocus.com/bid/28768