===================================================================
RCS file: /cvsrepo/anoncvs/cvs/src/usr.bin/ssh/PROTOCOL.u2f,v
retrieving revision 1.12
retrieving revision 1.13
diff -u -r1.12 -r1.13
--- src/usr.bin/ssh/PROTOCOL.u2f	2019/12/10 23:37:31	1.12
+++ src/usr.bin/ssh/PROTOCOL.u2f	2019/12/11 22:19:47	1.13
@@ -170,6 +170,10 @@
 	byte[]		extensions
 	byte[32]	SHA256(message)
 
+No extensons are yet defined for SSH use. If any are defined in the future,
+it will be possible to infer their presence from the contents of the "flags"
+value.
+
 The signature returned from U2F hardware takes the following format:
 
 	byte		flags (including "user present")