Add text regarding security advisories.

chapter01/changelog.xml

@@ -42,6 +42,16 @@
     <listitem revision="sysv"> or <listitem revision="systemd"> as
     appropriate for the entry or if needed the entire day's listitem.
     -->
+    <listitem>
+      <para>2021-07-19</para>
+      <itemizedlist>
+        <listitem>
+          <para>[renodr] - Add text about security advisories to the
+          Errata page.</para>
+        </listitem>
+      </itemizedlist>
+    </listitem>
+
     <listitem>
       <para>2021-07-17</para>
       <itemizedlist>

general.ent

@@ -31,6 +31,7 @@
 <!ENTITY livecd-root     "&lfs-root;livecd/">
 <!ENTITY test-results    "&lfs-root;lfs/build-logs/&generic-version;/">
 <!ENTITY errata          "&lfs-root;lfs/errata/&generic-version;/">
+<!ENTITY secadv          "&lfs-root;lfs/advisories/">
 <!ENTITY min-kernel      "3.2">
 
 <!ENTITY patches-rootd   "&lfs-root;patches/lfs/&generic-versiond;/">

prologue/errata.xml

@@ -8,7 +8,7 @@
 <sect1 id="pre-errata">
   <?dbhtml filename="errata.html"?>
 
-  <title>Errata</title>
+  <title>Errata and Security Advisories</title>
 
   <para>The software used to create an LFS system is constantly being updated
   and enhanced. Security warnings and bug fixes may become available after
@@ -21,4 +21,11 @@
   changes shown and apply them to the relevant section of the book as you
   progress with building the LFS system.</para>
 
+  <para>In addition, the Linux From Scratch editors maintain a list of security
+  vulnerabilities discovered after a book was released. To check whether there
+  are any active security vulnerabilities, please visit
+  <ulink url="&secadv;"/> prior to proceeding with your build. You should note
+  any advisories and perform the steps to fix any security vulnerabilities as
+  you progress with building the LFS system.</para>
+
 </sect1>