Added url that expains symlink vuln.

git-svn-id: http://svn.linuxfromscratch.org/LFS/trunk/BOOK@950 4aa44e1e-78dd-0310-a6d2-fbcd4c07a689

chapter06/ed-exp.xml

@@ -1,7 +1,8 @@
 <sect2>
 <title>Command explanations</title>
 
-<para><userinput>Insert proper symlink bug explanation here.</para>
-
-</sect2>
+<para>The sed commands fix a symlink vulnerability in ed. See
+<ulink url="http://www.securityfocus.com/templates/advisory.html?id=3308">
+http://www.securityfocus.com/templates/advisory.html?id=3308</ulink> for
+more information.</sect2>