Include bmcweb XSS disable in README

If bmcweb is hosting the webui then XSS needs
to be disabled to connect a local webui instance to
the BMC.

Change-Id: I538f657eed65939021120baa71c63728f2e6a828
Signed-off-by: Andrew Geissler <geissonator@yahoo.com>
diff --git a/README.md b/README.md
index f176529..01cd4d4 100644
--- a/README.md
+++ b/README.md
@@ -30,3 +30,8 @@
 ## Logging in
 Enter the BMC Host or BMC IP address, username, and password.
 The default username and password are `root`/`0penBmc`.
+
+**Note** that some OpenBMC implementations use [bmcweb](https://github.com/openbmc/bmcweb)
+for its backend. For security reasons, bmcweb will need to be recompiled and
+loaded onto the target BMC Host before the above redirect command will work. The
+option to turn on within bmcweb is `BMCWEB_INSECURE_DISABLE_XSS_PREVENTION`.