diff --git a/caps/include/nsNullPrincipal.h b/caps/include/nsNullPrincipal.h
index 10b83f3cfa0c..7e7b1c68bb58 100644
--- a/caps/include/nsNullPrincipal.h
+++ b/caps/include/nsNullPrincipal.h
@@ -16,6 +16,7 @@
 #include "nsJSPrincipals.h"
 #include "nsCOMPtr.h"
 #include "nsPrincipal.h"
+#include "nsIContentSecurityPolicy.h"
 
 class nsIURI;
 
@@ -53,6 +54,7 @@ public:
   virtual ~nsNullPrincipal();
 
   nsCOMPtr<nsIURI> mURI;
+  nsCOMPtr<nsIContentSecurityPolicy> mCSP;
 };
 
 #endif // nsNullPrincipal_h__
diff --git a/caps/src/nsNullPrincipal.cpp b/caps/src/nsNullPrincipal.cpp
index 9ff9730bc8df..639e064051fe 100644
--- a/caps/src/nsNullPrincipal.cpp
+++ b/caps/src/nsNullPrincipal.cpp
@@ -149,8 +149,11 @@ nsNullPrincipal::GetHashValue(uint32_t *aResult)
 NS_IMETHODIMP
 nsNullPrincipal::GetSecurityPolicy(void** aSecurityPolicy)
 {
-  // We don't actually do security policy caching.  And it's not like anyone
-  // can set a security policy for us anyway.
+  // Leftover from old security model, a "security policy" is a set of
+  // rules for property access that can override the SOP. Policies are
+  // associated with origins and since nsNullPinricipals never get the
+  // same origin twice, it's not possible to specify a "security
+  // policy" for it.  Hence, we do not cache the security policy.
   *aSecurityPolicy = nullptr;
   return NS_OK;
 }
@@ -158,8 +161,11 @@ nsNullPrincipal::GetSecurityPolicy(void** aSecurityPolicy)
 NS_IMETHODIMP
 nsNullPrincipal::SetSecurityPolicy(void* aSecurityPolicy)
 {
-  // We don't actually do security policy caching.  And it's not like anyone
-  // can set a security policy for us anyway.
+  // Leftover from old security model, a "security policy" is a set of
+  // rules for property access that can override the SOP. Policies are
+  // associated with origins and since nsNullPinricipals never get the
+  // same origin twice, it's not possible to specify a "security
+  // policy" for it.  Hence, we do not cache the security policy.
   return NS_OK;
 }
 
@@ -172,16 +178,20 @@ nsNullPrincipal::GetURI(nsIURI** aURI)
 NS_IMETHODIMP
 nsNullPrincipal::GetCsp(nsIContentSecurityPolicy** aCsp)
 {
-  // CSP on a null principal makes no sense
-  *aCsp = nullptr;
+  NS_IF_ADDREF(*aCsp = mCSP);
   return NS_OK;
 }
 
 NS_IMETHODIMP
 nsNullPrincipal::SetCsp(nsIContentSecurityPolicy* aCsp)
 {
-  // CSP on a null principal makes no sense
-  return NS_ERROR_NOT_AVAILABLE;
+  // If CSP was already set, it should not be destroyed!  Instead, it should
+  // get set anew when a new principal is created.
+  if (mCSP)
+    return NS_ERROR_ALREADY_INITIALIZED;
+
+  mCSP = aCsp;
+  return NS_OK;
 }
 
 NS_IMETHODIMP
diff --git a/content/base/src/contentSecurityPolicy.js b/content/base/src/contentSecurityPolicy.js
index f5be9abe93c7..03e7236a61d2 100644
--- a/content/base/src/contentSecurityPolicy.js
+++ b/content/base/src/contentSecurityPolicy.js
@@ -51,9 +51,9 @@ function ContentSecurityPolicy() {
 
   this._request = "";
   this._requestOrigin = "";
-  this._requestPrincipal = "";
+  this._weakRequestPrincipal =  { get : function() { return null; } };
   this._referrer = "";
-  this._docRequest = null;
+  this._weakDocRequest = { get : function() { return null; } };
   CSPdebug("CSP object initialized, no policies to enforce yet");
 
   this._cache = { };
@@ -296,7 +296,7 @@ ContentSecurityPolicy.prototype = {
       return;
 
     // Save the docRequest for fetching a policy-uri
-    this._docRequest = aChannel;
+    this._weakDocRequest = Cu.getWeakReference(aChannel);
 
     // save the document URI (minus <fragment>) and referrer for reporting
     let uri = aChannel.URI.cloneIgnoringRef();
@@ -307,8 +307,9 @@ ContentSecurityPolicy.prototype = {
     this._requestOrigin = uri;
 
     //store a reference to the principal, that can later be used in shouldLoad
-    this._requestPrincipal = Components.classes["@mozilla.org/scriptsecuritymanager;1"].
-    getService(Components.interfaces.nsIScriptSecurityManager).getChannelPrincipal(aChannel);
+    this._weakRequestPrincipal = Cu.getWeakReference(Cc["@mozilla.org/scriptsecuritymanager;1"]
+                                                       .getService(Ci.nsIScriptSecurityManager)
+                                                       .getChannelPrincipal(aChannel));
 
     if (aChannel.referrer) {
       let referrer = aChannel.referrer.cloneIgnoringRef();
@@ -358,13 +359,13 @@ ContentSecurityPolicy.prototype = {
       newpolicy = CSPRep.fromStringSpecCompliant(aPolicy,
                                                  selfURI,
                                                  aReportOnly,
-                                                 this._docRequest,
+                                                 this._weakDocRequest.get(),
                                                  this);
     } else {
       newpolicy = CSPRep.fromString(aPolicy,
                                     selfURI,
                                     aReportOnly,
-                                    this._docRequest,
+                                    this._weakDocRequest.get(),
                                     this);
     }
 
@@ -481,8 +482,8 @@ ContentSecurityPolicy.prototype = {
           // we need to set an nsIChannelEventSink on the channel object
           // so we can tell it to not follow redirects when posting the reports
           chan.notificationCallbacks = new CSPReportRedirectSink(policy);
-          if (this._docRequest) {
-            chan.loadGroup = this._docRequest.loadGroup;
+          if (this._weakDocRequest.get()) {
+            chan.loadGroup = this._weakDocRequest.get().loadGroup;
           }
 
           chan.QueryInterface(Ci.nsIUploadChannel)
@@ -501,7 +502,7 @@ ContentSecurityPolicy.prototype = {
                                   .getService(Ci.nsIContentPolicy);
             if (contentPolicy.shouldLoad(Ci.nsIContentPolicy.TYPE_CSP_REPORT,
                                          chan.URI, this._requestOrigin,
-                                         null, null, null, this._requestPrincipal)
+                                         null, null, null, this._weakRequestPrincipal.get())
                 != Ci.nsIContentPolicy.ACCEPT) {
               continue; // skip unauthorized URIs
             }
diff --git a/content/base/test/csp/file_bug886164.html b/content/base/test/csp/file_bug886164.html
new file mode 100644
index 000000000000..e47c2bc5da5a
--- /dev/null
+++ b/content/base/test/csp/file_bug886164.html
@@ -0,0 +1,15 @@
+<html>
+<head> <meta charset="utf-8"> </head>
+  <body>
+    <!-- sandbox="allow-same-origin" -->
+    <!-- Content-Security-Policy: default-src 'self' -->
+
+    <!-- these should be stopped by CSP -->
+    <img src="http://example.org/tests/content/base/test/csp/file_CSP.sjs?testid=img_bad&type=img/png"> </img>
+
+    <!-- these should load ok -->
+    <img src="/tests/content/base/test/csp/file_CSP.sjs?testid=img_good&type=img/png" />
+    <script src='/tests/content/base/test/csp/file_CSP.sjs?testid=scripta_bad&type=text/javascript'></script>
+
+  </body>
+</html>
diff --git a/content/base/test/csp/file_bug886164.html^headers^ b/content/base/test/csp/file_bug886164.html^headers^
new file mode 100644
index 000000000000..4c6fa3c26a77
--- /dev/null
+++ b/content/base/test/csp/file_bug886164.html^headers^
@@ -0,0 +1 @@
+Content-Security-Policy: default-src 'self'
diff --git a/content/base/test/csp/file_bug886164_2.html b/content/base/test/csp/file_bug886164_2.html
new file mode 100644
index 000000000000..f08826f698ff
--- /dev/null
+++ b/content/base/test/csp/file_bug886164_2.html
@@ -0,0 +1,14 @@
+<html>
+<head> <meta charset="utf-8"> </head>
+  <body>
+    <!-- sandbox -->
+    <!-- Content-Security-Policy: default-src 'self' -->
+
+    <!-- these should be stopped by CSP -->
+    <img src="http://example.org/tests/content/base/test/csp/file_CSP.sjs?testid=img2_bad&type=img/png"> </img>
+
+    <!-- these should load ok -->
+    <img src="/tests/content/base/test/csp/file_CSP.sjs?testid=img2a_good&type=img/png" />
+
+  </body>
+</html>
diff --git a/content/base/test/csp/file_bug886164_2.html^headers^ b/content/base/test/csp/file_bug886164_2.html^headers^
new file mode 100644
index 000000000000..4c6fa3c26a77
--- /dev/null
+++ b/content/base/test/csp/file_bug886164_2.html^headers^
@@ -0,0 +1 @@
+Content-Security-Policy: default-src 'self'
diff --git a/content/base/test/csp/file_bug886164_3.html b/content/base/test/csp/file_bug886164_3.html
new file mode 100644
index 000000000000..7cefd6569c86
--- /dev/null
+++ b/content/base/test/csp/file_bug886164_3.html
@@ -0,0 +1,12 @@
+<html>
+<head> <meta charset="utf-8"> </head>
+  <body>
+    <!-- sandbox -->
+    <!-- Content-Security-Policy: default-src 'none' -->
+
+    <!-- these should be stopped by CSP -->
+    <img src="http://example.org/tests/content/base/test/csp/file_CSP.sjs?testid=img3_bad&type=img/png"> </img>
+    <img src="/tests/content/base/test/csp/file_CSP.sjs?testid=img3a_bad&type=img/png" />
+
+  </body>
+</html>
diff --git a/content/base/test/csp/file_bug886164_3.html^headers^ b/content/base/test/csp/file_bug886164_3.html^headers^
new file mode 100644
index 000000000000..6581fd425ed9
--- /dev/null
+++ b/content/base/test/csp/file_bug886164_3.html^headers^
@@ -0,0 +1 @@
+Content-Security-Policy: default-src 'none'
diff --git a/content/base/test/csp/file_bug886164_4.html b/content/base/test/csp/file_bug886164_4.html
new file mode 100644
index 000000000000..146c6ba01fcd
--- /dev/null
+++ b/content/base/test/csp/file_bug886164_4.html
@@ -0,0 +1,12 @@
+<html>
+<head> <meta charset="utf-8"> </head>
+  <body>
+    <!-- sandbox -->
+    <!-- Content-Security-Policy: default-src 'none' -->
+
+    <!-- these should be stopped by CSP -->
+    <img src="http://example.org/tests/content/base/test/csp/file_CSP.sjs?testid=img4_bad&type=img/png"> </img>
+    <img src="/tests/content/base/test/csp/file_CSP.sjs?testid=img4a_bad&type=img/png" />
+
+  </body>
+</html>
diff --git a/content/base/test/csp/file_bug886164_4.html^headers^ b/content/base/test/csp/file_bug886164_4.html^headers^
new file mode 100644
index 000000000000..6581fd425ed9
--- /dev/null
+++ b/content/base/test/csp/file_bug886164_4.html^headers^
@@ -0,0 +1 @@
+Content-Security-Policy: default-src 'none'
diff --git a/content/base/test/csp/file_bug886164_5.html b/content/base/test/csp/file_bug886164_5.html
new file mode 100644
index 000000000000..1d9bd022c173
--- /dev/null
+++ b/content/base/test/csp/file_bug886164_5.html
@@ -0,0 +1,26 @@
+<!DOCTYPE HTML>
+<html>
+<head> <meta charset="utf-8"> </head>
+<script type="text/javascript">
+  function ok(result, desc) {
+    window.parent.postMessage({ok: result, desc: desc}, "*");
+  }
+
+  function doStuff() {
+    ok(true, "documents sandboxed with allow-scripts should be able to run inline scripts");
+  }
+</script>
+<script src='file_iframe_sandbox_pass.js'></script>
+<body onLoad='ok(true, "documents sandboxed with allow-scripts should be able to run script from event listeners");doStuff();'>
+  I am sandboxed but with only inline "allow-scripts"
+
+ <!-- sandbox="allow-scripts" -->
+ <!-- Content-Security-Policy: default-src 'none' 'unsafe-inline'-->
+
+ <!-- these should be stopped by CSP -->
+ <img src="/tests/content/base/test/csp/file_CSP.sjs?testid=img5_bad&type=img/png" />
+ <img src="http://example.org/tests/content/base/test/csp/file_CSP.sjs?testid=img5a_bad&type=img/png"> </img>
+ <script src='/tests/content/base/test/csp/file_CSP.sjs?testid=script5_bad&type=text/javascript'></script>
+ <script src='http://example.org/tests/content/base/test/csp/file_CSP.sjs?testid=script5a_bad&type=text/javascript'></script>
+</body>
+</html>
diff --git a/content/base/test/csp/file_bug886164_5.html^headers^ b/content/base/test/csp/file_bug886164_5.html^headers^
new file mode 100644
index 000000000000..3abc19055220
--- /dev/null
+++ b/content/base/test/csp/file_bug886164_5.html^headers^
@@ -0,0 +1 @@
+Content-Security-Policy: default-src 'none' 'unsafe-inline';
diff --git a/content/base/test/csp/file_bug886164_6.html b/content/base/test/csp/file_bug886164_6.html
new file mode 100644
index 000000000000..211a2aa06694
--- /dev/null
+++ b/content/base/test/csp/file_bug886164_6.html
@@ -0,0 +1,35 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <meta charset="utf-8">
+  <script type="text/javascript" src="/tests/SimpleTest/EventUtils.js"></script>
+</head>
+<script type="text/javascript">
+  function ok(result, desc) {
+    window.parent.postMessage({ok: result, desc: desc}, "*");
+  }
+
+  function doStuff() {
+    ok(true, "documents sandboxed with allow-scripts should be able to run inline scripts");
+
+    document.getElementById('a_form').submit();
+
+    // trigger the javascript: url test
+    sendMouseEvent({type:'click'}, 'a_link');
+  }
+</script>
+<script src='file_iframe_sandbox_pass.js'></script>
+<body onLoad='ok(true, "documents sandboxed with allow-scripts should be able to run script from event listeners");doStuff();'>
+  I am sandboxed but with "allow-scripts"
+  <img src="http://example.org/tests/content/base/test/csp/file_CSP.sjs?testid=img6_bad&type=img/png"> </img>
+  <script src='http://example.org/tests/content/base/test/csp/file_CSP.sjs?testid=script6_bad&type=text/javascript'></script>
+
+  <form method="get" action="file_iframe_sandbox_form_fail.html" id="a_form">
+    First name: <input type="text" name="firstname">
+    Last name: <input type="text" name="lastname">
+    <input type="submit" onclick="doSubmit()" id="a_button">
+  </form>
+
+  <a href = 'javascript:ok(true, "documents sandboxed with allow-scripts should be able to run script from javascript: URLs");' id='a_link'>click me</a>
+</body>
+</html>
diff --git a/content/base/test/csp/file_bug886164_6.html^headers^ b/content/base/test/csp/file_bug886164_6.html^headers^
new file mode 100644
index 000000000000..6f9fc3f25de2
--- /dev/null
+++ b/content/base/test/csp/file_bug886164_6.html^headers^
@@ -0,0 +1 @@
+Content-Security-Policy: default-src 'self' 'unsafe-inline';
diff --git a/content/base/test/csp/mochitest.ini b/content/base/test/csp/mochitest.ini
index 42b7767a1b7a..fc9dcc91222e 100644
--- a/content/base/test/csp/mochitest.ini
+++ b/content/base/test/csp/mochitest.ini
@@ -68,6 +68,18 @@ support-files =
   file_bug836922_npolicies.html^headers^
   file_bug836922_npolicies_ro_violation.sjs
   file_bug836922_npolicies_violation.sjs
+  file_bug886164.html
+  file_bug886164.html^headers^
+  file_bug886164_2.html
+  file_bug886164_2.html^headers^
+  file_bug886164_3.html
+  file_bug886164_3.html^headers^
+  file_bug886164_4.html
+  file_bug886164_4.html^headers^
+  file_bug886164_5.html
+  file_bug886164_5.html^headers^
+  file_bug886164_6.html
+  file_bug886164_6.html^headers^
   file_csp_bug768029.html
   file_csp_bug768029.sjs
   file_csp_bug773891.html
@@ -101,6 +113,7 @@ support-files =
 [test_CSP_inlinestyle.html]
 [test_bothCSPheaders.html]
 [test_bug836922_npolicies.html]
+[test_bug886164.html]
 [test_csp_redirects.html]
 [test_CSP_bug910139.html]
 [test_CSP_bug909029.html]
diff --git a/content/base/test/csp/test_bug886164.html b/content/base/test/csp/test_bug886164.html
new file mode 100644
index 000000000000..3cdea4ca1e9e
--- /dev/null
+++ b/content/base/test/csp/test_bug886164.html
@@ -0,0 +1,183 @@
+<!DOCTYPE HTML>
+<html>
+<head>
+  <meta charset="utf-8">
+  <title>Bug 886164 - Enforce CSP in sandboxed iframe</title>
+  <script type="text/javascript" src="/tests/SimpleTest/SimpleTest.js"></script>
+  <link rel="stylesheet" type="text/css" href="/tests/SimpleTest/test.css" />
+</head>
+<body>
+<p id="display"></p>
+<div id="content" style="display: none">
+
+
+</div>
+
+<iframe style="width:200px;height:200px;" id='cspframe'  sandbox="allow-same-origin"></iframe>
+<iframe style="width:200px;height:200px;" id='cspframe2' sandbox></iframe>
+<iframe style="width:200px;height:200px;" id='cspframe3' sandbox="allow-same-origin"></iframe>
+<iframe style="width:200px;height:200px;" id='cspframe4' sandbox></iframe>
+<iframe style="width:200px;height:200px;" id='cspframe5' sandbox="allow-scripts"></iframe>
+<iframe style="width:200px;height:200px;" id='cspframe6' sandbox="allow-same-origin allow-scripts"></iframe>
+<script class="testbody" type="text/javascript">
+
+
+var path = "/tests/content/base/test/csp/";
+
+// These are test results: -1 means it hasn't run,
+// true/false is the pass/fail result.
+window.tests = {
+  // sandbox allow-same-origin; 'self'
+  img_good: -1, // same origin
+  img_bad: -1, //example.com
+
+  // sandbox; 'self'
+  img2_bad: -1, //example.com
+  img2a_good: -1, // same origin & is image
+
+  // sandbox allow-same-origin; 'none'
+  img3_bad: -1,
+  img3a_bad: -1,
+
+  // sandbox; 'none'
+  img4_bad: -1,
+  img4a_bad: -1,
+
+  // sandbox allow-scripts; 'none' 'unsafe-inline'
+  img5_bad: -1,
+  img5a_bad: -1,
+  script5_bad: -1,
+  script5a_bad: -1,
+
+  // sandbox allow-same-origin allow-scripts; 'self' 'unsafe-inline'
+  img6_bad: -1,
+  script6_bad: -1,
+};
+
+// a postMessage handler that is used by sandboxed iframes without
+// 'allow-same-origin' to communicate pass/fail back to this main page.
+// it expects to be called with an object like {ok: true/false, desc:
+// <description of the test> which it then forwards to ok()
+window.addEventListener("message", receiveMessage, false);
+
+function receiveMessage(event)
+{
+  ok_wrapper(event.data.ok, event.data.desc);
+}
+
+var cspTestsDone = false;
+var iframeSandboxTestsDone = false;
+
+// iframe related
+var completedTests = 0;
+var passedTests = 0;
+
+function ok_wrapper(result, desc) {
+  ok(result, desc);
+
+  completedTests++;
+
+  if (result) {
+    passedTests++;
+  }
+
+  if (completedTests === 5) {
+    iframeSandboxTestsDone = true;
+    if (cspTestsDone) {
+      SimpleTest.finish();
+    }
+  }
+}
+
+
+//csp related
+
+// This is used to watch the blocked data bounce off CSP and allowed data
+// get sent out to the wire.
+function examiner() {
+  SpecialPowers.addObserver(this, "csp-on-violate-policy", false);
+  SpecialPowers.addObserver(this, "http-on-modify-request", false);
+}
+examiner.prototype  = {
+  observe: function(subject, topic, data) {
+    // subject should be an nsURI, and should be either allowed or blocked.
+    if (!SpecialPowers.can_QI(subject))
+      return;
+
+    var testpat = new RegExp("testid=([a-z0-9_]+)");
+
+    //_good things better be allowed!
+    //_bad things better be stopped!
+
+    if (topic === "http-on-modify-request") {
+      //these things were allowed by CSP
+      var asciiSpec = SpecialPowers.getPrivilegedProps(SpecialPowers.do_QueryInterface(subject, "nsIHttpChannel"), "URI.asciiSpec");
+      if (!testpat.test(asciiSpec)) return;
+      var testid = testpat.exec(asciiSpec)[1];
+
+      window.testResult(testid,
+                        /_good/.test(testid),
+                        asciiSpec + " allowed by csp");
+    }
+
+    if(topic === "csp-on-violate-policy") {
+      //these were blocked... record that they were blocked
+      var asciiSpec = SpecialPowers.getPrivilegedProps(SpecialPowers.do_QueryInterface(subject, "nsIURI"), "asciiSpec");
+      if (!testpat.test(asciiSpec)) return;
+      var testid = testpat.exec(asciiSpec)[1];
+      window.testResult(testid,
+                        /_bad/.test(testid),
+                        asciiSpec + " blocked by \"" + data + "\"");
+    }
+  },
+
+  // must eventually call this to remove the listener,
+  // or mochitests might get borked.
+  remove: function() {
+    SpecialPowers.removeObserver(this, "csp-on-violate-policy");
+    SpecialPowers.removeObserver(this, "http-on-modify-request");
+  }
+}
+
+window.examiner = new examiner();
+
+window.testResult = function(testname, result, msg) {
+  //test already complete.... forget it... remember the first result.
+  if (window.tests[testname] != -1)
+    return;
+
+  window.tests[testname] = result;
+  ok(result, testname + ' test: ' + msg);
+
+  // if any test is incomplete, keep waiting
+  for (var v in window.tests)
+    if(tests[v] == -1)
+      return;
+
+  // ... otherwise, finish
+  window.examiner.remove();
+  cspTestsDone = true;
+  if (iframeSandboxTestsDone) {
+    SimpleTest.finish();
+  }
+}
+
+SimpleTest.waitForExplicitFinish();
+
+SpecialPowers.pushPrefEnv(
+  {'set':[["security.csp.speccompliant", true]]},
+  function() {
+    // save this for last so that our listeners are registered.
+    // ... this loads the testbed of good and bad requests.
+    document.getElementById('cspframe').src = 'file_bug886164.html';
+    document.getElementById('cspframe2').src = 'file_bug886164_2.html';
+    document.getElementById('cspframe3').src = 'file_bug886164_3.html';
+    document.getElementById('cspframe4').src = 'file_bug886164_4.html';
+    document.getElementById('cspframe5').src = 'file_bug886164_5.html';
+    document.getElementById('cspframe6').src = 'file_bug886164_6.html';
+  });
+
+</script>
+</pre>
+</body>
+</html>
diff --git a/testing/mochitest/b2g.json b/testing/mochitest/b2g.json
index d2762dbdf28b..90eeee181578 100644
--- a/testing/mochitest/b2g.json
+++ b/testing/mochitest/b2g.json
@@ -209,6 +209,7 @@
     "content/base/test/csp/test_CSP_frameancestors.html":"observer not working",
     "content/base/test/csp/test_CSP.html":"observer not working",
     "content/base/test/csp/test_bug836922_npolicies.html":"observer not working",
+    "content/base/test/csp/test_bug886164.html":"observer not working",
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