Add a Handbook section about HTTP Pings. https://redmine.stoutner.com/issues/976

diff --git a/doc/index.docbook b/doc/index.docbook
index c519d0e5f81c13ae7f7ea6a4bf937c970f1b711c..0d0e6f8ff3f967cb1563a5a35677a0ba98a6e415 100644 (file)
--- a/doc/index.docbook
+++ b/doc/index.docbook
@@ -302,6 +302,25 @@
       </para>
     </sect1>
 
+    <!-- HTTP Pings. -->
+    <sect1 id="http-pings">
+      <title>HTTP Pings</title>
+
+      <para>
+        HTTP hyperlinks can have an extra <ulink url="https://developer.mozilla.org/en-US/docs/Web/HTML/Element/a#ping">ping attribute</ulink> that sends a POST request to a different URL.
+        These HTTP pings are commonly used for tracking.
+        <ulink url="https://www.theregister.com/2019/04/06/apple_safari_changes/">Most browsers</ulink> send HTTP pings without informing the user
+        <ulink url="https://lists.w3.org/Archives/Public/public-html/2018May/0027.html">in any way</ulink>
+        (despite what The Register article says, current versions of FireFox also happily send HTTP pings).
+      </para>
+
+      <para>
+        Privacy Browser blocks all HTTP pings and presents a dialog informing the user every time the current tab attempts to send one.
+        Hopefully, as more people become aware of what HTTP pings are, web sites will become more embarrassed about using them.
+        This is a classic example of how those who wrote the HTTP specs do not have the best interests of internet users at heart. I would like the day to come where they are removed from the specs.
+      </para>
+    </sect1>
+
     <!-- Spell Checking. -->
     <sect1 id="spell-checking">
       <title>Spell Checking</title>