Fixed CVE-2017-12794 -- Fixed XSS possibility in traceback section of technical 500 debug page.

This is a security fix.

5 files changed, 35 insertions, 19 deletions

diff --git a/django/views/debug.py b/django/views/debug.py
index fca137fd07..35cff6338f 100644
--- a/django/views/debug.py
+++ b/django/views/debug.py
@@ -8,7 +8,7 @@ from pathlib import Path
 from django.conf import settings
 from django.http import HttpResponse, HttpResponseNotFound
 from django.template import Context, Engine, TemplateDoesNotExist
-from django.template.defaultfilters import force_escape, pprint
+from django.template.defaultfilters import pprint
 from django.urls import Resolver404, resolve
 from django.utils import timezone
 from django.utils.datastructures import MultiValueDict
@@ -271,7 +271,7 @@ class ExceptionReporter:
                     # Trim large blobs of data
                     if len(v) > 4096:
                         v = '%s... <trimmed %d bytes string>' % (v[0:4096], len(v))
-                    frame_vars.append((k, force_escape(v)))
+                    frame_vars.append((k, v))
                 frame['vars'] = frame_vars
             frames[i] = frame
 
diff --git a/django/views/templates/technical_500.html b/django/views/templates/technical_500.html
index 01534f80d9..25cf231ead 100644
--- a/django/views/templates/technical_500.html
+++ b/django/views/templates/technical_500.html
@@ -212,38 +212,37 @@
   <h2>Traceback <span class="commands">{% if not is_email %}<a href="#" onclick="return switchPastebinFriendly(this);">
     Switch to copy-and-paste view</a></span>{% endif %}
   </h2>
-  {% autoescape off %}
   <div id="browserTraceback">
     <ul class="traceback">
       {% for frame in frames %}
         {% ifchanged frame.exc_cause %}{% if frame.exc_cause %}
           <li><h3>
           {% if frame.exc_cause_explicit %}
-            The above exception ({{ frame.exc_cause }}) was the direct cause of the following exception:
+            The above exception ({{ frame.exc_cause|force_escape }}) was the direct cause of the following exception:
           {% else %}
-            During handling of the above exception ({{ frame.exc_cause }}), another exception occurred:
+            During handling of the above exception ({{ frame.exc_cause|force_escape }}), another exception occurred:
           {% endif %}
         </h3></li>
         {% endif %}{% endifchanged %}
         <li class="frame {{ frame.type }}">
-          <code>{{ frame.filename|escape }}</code> in <code>{{ frame.function|escape }}</code>
+          <code>{{ frame.filename }}</code> in <code>{{ frame.function }}</code>
 
           {% if frame.context_line %}
             <div class="context" id="c{{ frame.id }}">
               {% if frame.pre_context and not is_email %}
                 <ol start="{{ frame.pre_context_lineno }}" class="pre-context" id="pre{{ frame.id }}">
                 {% for line in frame.pre_context %}
-                  <li onclick="toggle('pre{{ frame.id }}', 'post{{ frame.id }}')"><pre>{{ line|escape }}</pre></li>
+                  <li onclick="toggle('pre{{ frame.id }}', 'post{{ frame.id }}')"><pre>{{ line }}</pre></li>
                 {% endfor %}
                 </ol>
               {% endif %}
               <ol start="{{ frame.lineno }}" class="context-line">
-                <li onclick="toggle('pre{{ frame.id }}', 'post{{ frame.id }}')"><pre>{{ frame.context_line|escape }}</pre>{% if not is_email %} <span>...</span>{% endif %}</li>
+                <li onclick="toggle('pre{{ frame.id }}', 'post{{ frame.id }}')"><pre>{{ frame.context_line }}</pre>{% if not is_email %} <span>...</span>{% endif %}</li>
               </ol>
               {% if frame.post_context and not is_email  %}
                 <ol start='{{ frame.lineno|add:"1" }}' class="post-context" id="post{{ frame.id }}">
                   {% for line in frame.post_context %}
-                  <li onclick="toggle('pre{{ frame.id }}', 'post{{ frame.id }}')"><pre>{{ line|escape }}</pre></li>
+                  <li onclick="toggle('pre{{ frame.id }}', 'post{{ frame.id }}')"><pre>{{ line }}</pre></li>
                   {% endfor %}
               </ol>
               {% endif %}
@@ -268,7 +267,7 @@
               <tbody>
                 {% for var in frame.vars|dictsort:0 %}
                   <tr>
-                    <td>{{ var.0|force_escape }}</td>
+                    <td>{{ var.0 }}</td>
                     <td class="code"><pre>{{ var.1 }}</pre></td>
                   </tr>
                 {% endfor %}
@@ -279,7 +278,6 @@
       {% endfor %}
     </ul>
   </div>
-  {% endautoescape %}
   <form action="http://dpaste.com/" name="pasteform" id="pasteform" method="post">
 {% if not is_email %}
   <div id="pastebinTraceback" class="pastebin">
@@ -318,9 +316,9 @@ In template {{ template_info.name }}, error at line {{ template_info.line }}
 
 Traceback:{% for frame in frames %}
 {% ifchanged frame.exc_cause %}{% if frame.exc_cause %}{% if frame.exc_cause_explicit %}
-The above exception ({{ frame.exc_cause }}) was the direct cause of the following exception:
+The above exception ({{ frame.exc_cause|force_escape }}) was the direct cause of the following exception:
 {% else %}
-During handling of the above exception ({{ frame.exc_cause }}), another exception occurred:
+During handling of the above exception ({{ frame.exc_cause|force_escape }}), another exception occurred:
 {% endif %}{% endif %}{% endifchanged %}
 File "{{ frame.filename }}" in {{ frame.function }}
 {% if frame.context_line %}  {{ frame.lineno }}. {{ frame.context_line }}{% endif %}{% endfor %}
diff --git a/docs/releases/1.10.8.txt b/docs/releases/1.10.8.txt
index 160e555fef..3785e6535a 100644
--- a/docs/releases/1.10.8.txt
+++ b/docs/releases/1.10.8.txt
@@ -5,3 +5,12 @@ Django 1.10.8 release notes
 *September 5, 2017*
 
 Django 1.10.8 fixes a security issue in 1.10.7.
+
+CVE-2017-12794: Possible XSS in traceback section of technical 500 debug page
+=============================================================================
+
+In older versions, HTML autoescaping was disabled in a portion of the template
+for the technical 500 debug page. Given the right circumstances, this allowed
+a cross-site scripting attack. This vulnerability shouldn't affect most
+production sites since you shouldn't run with ``DEBUG = True`` (which makes
+this page accessible) in your production settings.
diff --git a/docs/releases/1.11.5.txt b/docs/releases/1.11.5.txt
index c0af25fb43..dda3489b93 100644
--- a/docs/releases/1.11.5.txt
+++ b/docs/releases/1.11.5.txt
@@ -6,6 +6,15 @@ Django 1.11.5 release notes
 
 Django 1.11.5 fixes a security issue and several bugs in 1.11.4.
 
+CVE-2017-12794: Possible XSS in traceback section of technical 500 debug page
+=============================================================================
+
+In older versions, HTML autoescaping was disabled in a portion of the template
+for the technical 500 debug page. Given the right circumstances, this allowed
+a cross-site scripting attack. This vulnerability shouldn't affect most
+production sites since you shouldn't run with ``DEBUG = True`` (which makes
+this page accessible) in your production settings.
+
 Bugfixes
 ========
 
diff --git a/tests/view_tests/tests/test_debug.py b/tests/view_tests/tests/test_debug.py
index 8de484d6a9..71c60210e4 100644
--- a/tests/view_tests/tests/test_debug.py
+++ b/tests/view_tests/tests/test_debug.py
@@ -349,10 +349,10 @@ class ExceptionReporterTests(SimpleTestCase):
         request = self.rf.get('/test_view/')
         try:
             try:
-                raise AttributeError('Top level')
+                raise AttributeError(mark_safe('<p>Top level</p>'))
             except AttributeError as explicit:
                 try:
-                    raise ValueError('Second exception') from explicit
+                    raise ValueError(mark_safe('<p>Second exception</p>')) from explicit
                 except ValueError:
                     raise IndexError(mark_safe('<p>Final exception</p>'))
         except Exception:
@@ -366,13 +366,13 @@ class ExceptionReporterTests(SimpleTestCase):
         html = reporter.get_traceback_html()
         # Both messages are twice on page -- one rendered as html,
         # one as plain text (for pastebin)
-        self.assertEqual(2, html.count(explicit_exc.format("Top level")))
-        self.assertEqual(2, html.count(implicit_exc.format("Second exception")))
+        self.assertEqual(2, html.count(explicit_exc.format('&lt;p&gt;Top level&lt;/p&gt;')))
+        self.assertEqual(2, html.count(implicit_exc.format('&lt;p&gt;Second exception&lt;/p&gt;')))
         self.assertEqual(10, html.count('&lt;p&gt;Final exception&lt;/p&gt;'))
 
         text = reporter.get_traceback_text()
-        self.assertIn(explicit_exc.format("Top level"), text)
-        self.assertIn(implicit_exc.format("Second exception"), text)
+        self.assertIn(explicit_exc.format('<p>Top level</p>'), text)
+        self.assertIn(implicit_exc.format('<p>Second exception</p>'), text)
         self.assertEqual(3, text.count('<p>Final exception</p>'))
 
     def test_reporting_frames_without_source(self):