Merge #1033: pages: add Security Advisories

593e740 pages: add Security Advisories (fanquake)

Pull request description:

  Add a new page summarizing the upcoming security advisory policy.

  ![advisories](https://github.com/bitcoin-core/bitcoincore.org/assets/863730/b0e9b765-e74a-4909-8ab0-a20fdedeaaeb)

ACKs for top commit:
  sipa:
    ACK 593e740
  dergoegge:
    ACK 593e740
  darosior:
    ACK 593e740

Tree-SHA512: 7dda08c75890390c09486f6f53ab56fb7101b03ec713f8289f9398773c6c1e1f310d6254ed60d334c2d5fb58df5fa027627350f7d50cf34aac34740922950f98

Author: fanquake

_data/navigation.yml

@@ -31,6 +31,9 @@ en:
       eol:
         title: "Lifecycle"
         url:   "/en/lifecycle"
+      disclosures:
+        title: "Security Advisories"
+        url: "/en/security-advisories/"
   contact:
     title: "Contact"
     submenu: true

_posts/en/pages/2024-06-26-disclosures.md

@@ -0,0 +1,50 @@
+---
+title: Security Advisories
+name: Security Advisories
+id: en-security-advisories
+permalink: /en/security-advisories/
+layout: page
+type: pages
+lang: en
+version: 1
+---
+{% include toc.html %}
+
+This page summarizes policies in relation to disclosing vulnerabilities in Bitcoin Core,
+as well as provides a summary of historical Security Advisories.
+
+## Policy
+
+When reported, a vulnerability will be assigned a severity category. We
+differentiate between 4 classes of vulnerabilities:
+
+* **Low**: bugs which are hard to exploit or have a low impact. For instance
+  a wallet bug which requires access to the victim's machine.
+
+* **Medium**: bugs with limited impact. For instance a local network remote crash.
+
+* **High**: bugs with significant impact. For instance a remote crash, or a local network RCE.
+
+* **Critical**: bugs which threaten the whole network's integrity. For instance an inflation or coin theft bug.
+
+**Low** severity bugs will be disclosed 2 weeks after a fixed version is released.
+  A pre-announcement will be made at the same time as the release.
+
+**Medium** and **High** severity bugs will be disclosed 2 weeks after the [last
+  affected release goes EOL](/en/lifecycle/). This is a year after a fixed version was first
+  released. A pre-announcement will be made 2 weeks prior to disclosure.
+
+**Critical** bugs are not considered in the standard policy, as they would most likely require an
+  ad-hoc procedure. Also, a bug may not be considered a vulnerability at all. Any reported issue
+  may also be considered serious, yet not require embargo.
+
+## Past Security Advisories
+
+{% assign disclosures=site.posts | where:"lang", 'en' | where:"type", 'disclosure' %}
+{% for default_disclosure in disclosures %}
+{% assign post=default_disclosure %}
+  <article>
+    <h2><a href="{{ post.url }}" title="{{ post.title | xml_escape }}">{{ post.title }}</a></h2>
+    <p>{{ post.excerpt | markdownify | strip_html | truncate: 200 }}</p>
+  </article>
+{% endfor %}