diff --git a/mozilla/caps/idl/nsIScriptSecurityManager.idl b/mozilla/caps/idl/nsIScriptSecurityManager.idl
index 521281c3095..a102b40eee8 100644
--- a/mozilla/caps/idl/nsIScriptSecurityManager.idl
+++ b/mozilla/caps/idl/nsIScriptSecurityManager.idl
@@ -198,6 +198,12 @@ interface nsIScriptSecurityManager : nsIXPCSecurityManager
     [noscript] nsIPrincipal getObjectPrincipal(in JSContextPtr cx,
                                                in JSObjectPtr obj);
 
+    /**
+     * Returns true if the principal of the currently running script is the
+     * system principal, false otherwise.
+     */
+    boolean subjectPrincipalIsSystem();
+
     /**
      * Forget all currently stored security policies and reread from prefs.
      * This must be called after any capability.policy prefs have changed.
diff --git a/mozilla/caps/src/nsScriptSecurityManager.cpp b/mozilla/caps/src/nsScriptSecurityManager.cpp
index df27be9b0a5..ac4d940ff46 100644
--- a/mozilla/caps/src/nsScriptSecurityManager.cpp
+++ b/mozilla/caps/src/nsScriptSecurityManager.cpp
@@ -1248,6 +1248,31 @@ nsScriptSecurityManager::GetSystemPrincipal(nsIPrincipal **result)
     return NS_OK;
 }
 
+NS_IMETHODIMP
+nsScriptSecurityManager::SubjectPrincipalIsSystem(PRBool* aIsSystem)
+{
+    NS_ENSURE_ARG_POINTER(aIsSystem);
+    *aIsSystem = PR_FALSE;
+
+    if (!mSystemPrincipal)
+        return NS_OK;
+
+    nsCOMPtr<nsIPrincipal> subject;
+    nsresult rv = GetSubjectPrincipal(getter_AddRefs(subject));
+    if (NS_FAILED(rv))
+        return rv;
+
+    if(!subject)
+    {
+        // No subject principal means no JS is running;
+        // this is the equivalent of system principal code
+        *aIsSystem = PR_TRUE;
+        return NS_OK;
+    }
+
+    return mSystemPrincipal->Equals(subject, aIsSystem);
+}
+
 NS_IMETHODIMP
 nsScriptSecurityManager::GetCertificatePrincipal(const char* aCertID,
                                                  nsIPrincipal **result)
@@ -2708,7 +2733,6 @@ nsScriptSecurityManager::InitPrefs()
     PRUint32 prefCount;
     char** prefNames;
 
-    //-- Set a callback for policy changes
     // Registering the security manager as an observer to the
     // profile-after-change topic. We will build up the policy table
     // after the initial profile loads and after profile switches.
diff --git a/mozilla/dom/src/base/nsGlobalWindow.cpp b/mozilla/dom/src/base/nsGlobalWindow.cpp
index 27de3ef1e27..1a74a58ce0d 100644
--- a/mozilla/dom/src/base/nsGlobalWindow.cpp
+++ b/mozilla/dom/src/base/nsGlobalWindow.cpp
@@ -1194,6 +1194,18 @@ NS_IMETHODIMP
 GlobalWindowImpl::GetOpener(nsIDOMWindowInternal** aOpener)
 {
   *aOpener = nsnull;
+  // First, check if we were called from a privileged chrome script
+  nsCOMPtr<nsIScriptSecurityManager> secMan(
+      do_GetService(NS_SCRIPTSECURITYMANAGER_CONTRACTID));
+  NS_ENSURE_TRUE(secMan, NS_ERROR_FAILURE);
+  PRBool inChrome;
+  nsresult rv = secMan->SubjectPrincipalIsSystem(&inChrome);
+  if (NS_SUCCEEDED(rv) && inChrome) {
+    *aOpener = mOpener;
+    NS_IF_ADDREF(*aOpener);
+    return NS_OK;
+  }
+
   // We don't want to reveal the opener if the opener is a mail window,
   // because opener can be used to spoof the contents of a message (bug 105050).
   // So, we look in the opener's root docshell to see if it's a mail window.