doc: suggest security@golang.org for reporting security issues

Fixes #11402

Change-Id: I195575a54e30ad6d6b1d0996fde34c0163bbd2c2
Reviewed-on: https://go-review.googlesource.com/11530
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
diff --git a/doc/contrib.html b/doc/contrib.html
index 93a609f..c286abc 100644
--- a/doc/contrib.html
+++ b/doc/contrib.html
@@ -91,6 +91,10 @@
 We pride ourselves on being meticulous; no issue is too small.
 </p>
 
+<p>
+Sensitive security-related issues should be reported to <a href="mailto:security@golang.org">security@golang.org</a>.
+</p>
+
 <h3><a href="/doc/contribute.html">Contributing code</a></h3>
 
 <p>