update security.md (#7528)

SECURITY.md

@@ -1,15 +1,10 @@
-# TEST Security Policy
-
-## Supported Versions
-
-Use this section to tell people about which versions of your project are
-currently being supported with security updates.
-
+# Security Policy
 
 ## Reporting a Vulnerability
 
-Use this section to tell people how to report a vulnerability.
+To report a suspected security-related vulnerability within [MDN Web Docs](https://developer.mozilla.org), please use
+[this Bugzilla link](https://bugzilla.mozilla.org/enter_bug.cgi?product=developer.mozilla.org&component=Security), **and before submitting**, it is important to click the checkbox, just above the `Submit` button, entitled:
 
-Tell them where to go, how often they can expect to get an update on a
-reported vulnerability, what to expect if the vulnerability is accepted or
-declined, etc.
+```
+This report is about a problem that is putting users at risk. It should be kept hidden from the public until it is resolved.
+```