upstream: add some cautionary text about % token expansion and

shell metacharacters; based on report from vinci AT protonmail.ch

OpenBSD-Commit-ID: aa1450a54fcee2f153ef70368d90edb1e7019113

Author: djmdjm

ssh_config.5

@@ -33,8 +33,8 @@
 .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 .\"
-.\" $OpenBSD: ssh_config.5,v 1.386 2023/08/28 09:52:09 djm Exp $
-.Dd $Mdocdate: August 28 2023 $
+.\" $OpenBSD: ssh_config.5,v 1.387 2023/10/04 04:03:50 djm Exp $
+.Dd $Mdocdate: October 4 2023 $
 .Dt SSH_CONFIG 5
 .Os
 .Sh NAME
@@ -2206,6 +2206,16 @@ accepts all tokens.
 and
 .Cm ProxyJump
 accept the tokens %%, %h, %n, %p, and %r.
+.Pp
+Note that some of these directives build commands for execution via the shell.
+Because
+.Xr ssh 1
+performs no filtering or escaping of characters that have special meaning in
+shell commands (e.g. quotes), it is the user's reposibility to ensure that
+the arguments passed to
+.Xr ssh 1
+do not contain such characters and that tokens are appropriately quoted
+when used.
 .Sh ENVIRONMENT VARIABLES
 Arguments to some keywords can be expanded at runtime from environment
 variables on the client by enclosing them in