doc: june 2018 sec pre-announce (#1680)

Add blog for June 2018 pre-announce
Update header to point to pre-announce

build.js

@@ -254,9 +254,9 @@ function getSource (callback) {
           lts: latestVersion.lts(versions)
         },
         banner: {
-          visible: false,
-          text: 'Important March 2018 security upgrades now available',
-          link: '/en/blog/vulnerability/march-2018-security-releases/'
+          visible: true,
+          text: 'June 2018 Security Releases',
+          link: '/en/blog/vulnerability/june-2018-security-releases/'
         }
       }
     }

locale/en/blog/vulnerability/june-2018-security-releases.md

@@ -0,0 +1,32 @@
+---
+date: 2018-06-06T03:18:59.230Z
+category: vulnerability
+title: June 2018 Security Releases
+slug: june-2018-security-releases
+layout: blog-post.hbs
+author: Michael Dawson
+---
+
+# Summary
+
+Node.js will release new versions of all supported release lines on or around June 12th, 2018 (UTC). These releases will incorporate a number of security fixes.
+
+# Impact
+
+* All versions of Node.js 6.x (LTS "Boron") are vulnerable to 1 denial-of-service (DoS) vulnerability with a severity of LOW.
+* All versions of Node.js 8.x (LTS "Carbon") are vulnerable to 2 denial-of-service (DoS) vulnerabilities, the highest severity being HIGH.
+* Versions of Node.js 9.x are vulnerable to 5 denial-of-service (DoS) vulnerabilities, the highest severity being HIGH.
+* All versions of Node.js 10.x (Current) are vulnerable to 4 denial-of-service (DoS) vulnerabilities, the highest severity being HIGH.
+
+# Release timing
+
+Releases will be available on or around June 12th, 2018 (UTC), along with disclosure of the details for the flaws addressed in each release in order to allow for complete impact assessment by users.
+
+# Contact and future updates
+
+The current Node.js security policy can be found at https://nodejs.org/en/security/.
+
+Please contact security@nodejs.org if you wish to report a vulnerability in Node.js.
+
+Subscribe to the low-volume announcement-only nodejs-sec mailing list at https://groups.google.com/forum/#!forum/nodejs-sec to stay up to date on security vulnerabilities and security-related releases of Node.js and the projects maintained in the [nodejs GitHub organization](https://github.com/nodejs/).
+