Merge branch 'feature/xhtml-im-security-considerations' of https://github.com/horazont/xeps into feature/xep-0071

xep-0071.xml

@@ -36,6 +36,12 @@
     <url>http://www.xmpp.org/schemas/xhtml-im-model.xsd</url>
   </schemaloc>
   &stpeter;
+  <revision>
+    <version>1.5.2</version>
+    <date>2017-10-12</date>
+    <initials>jwi</initials>
+    <remark><p>Clarify security considerations.</p></remark>
+  </revision>
   <revision>
     <version>1.5.1</version>
     <date>2016-01-05</date>
@@ -838,7 +844,8 @@ That seems fine to me.
 </section1>
 <section1 topic='Security Considerations' anchor='security'>
   <section2 topic='Malicious Objects' anchor='security-code'>
-    <p>The exclusion of scripts, applets, binary objects, and other potentially executable code from XHTML-IM reduces the risk of exposure to harmful or malicious objects caused by inclusion of XHTML content. To further reduce the risk of such exposure, an implementation MAY choose to:</p>
+    <p>While scripts, applets, binary objects and other potentially executable code is excluded from the profiles used in XHTML-IM, malicious entities still may inject those and thus exploit entities which rely on this exclusion. Entities thus MUST assume that inbound XHTML-IM may be mailicious and MUST sanitize it according to the profile used, by ignoring elements and removing attributes as needed.</p>
+    <p>To further reduce the risk of such exposure, an implementation MAY choose to:</p>
     <ul>
       <li>Not make hyperlinks clickable</li>
       <li>Not fetch or present images but instead show only the 'alt' text.</li>