2 files changed, 40 insertions, 1 deletions
diff --git a/dom/base/nsDocument.cpp b/dom/base/nsDocument.cpp
index 6c97750b9..9043e409a 100644
--- a/dom/base/nsDocument.cpp
+++ b/dom/base/nsDocument.cpp
@@ -1329,7 +1329,8 @@ nsIDocument::nsIDocument()
     mFrameRequestCallbacksScheduled(false),
     mBidiOptions(IBMBIDI_DEFAULT_BIDI_OPTIONS),
     mPartID(0),
-    mUserHasInteracted(false)
+    mUserHasInteracted(false),
+    mThrowOnDynamicMarkupInsertionCounter(0)
 {
   SetIsInDocument();
 
diff --git a/dom/base/nsIDocument.h b/dom/base/nsIDocument.h
index 66f30a6bc..364583c88 100644
--- a/dom/base/nsIDocument.h
+++ b/dom/base/nsIDocument.h
@@ -2879,6 +2879,22 @@ public:
   virtual void ScheduleIntersectionObserverNotification() = 0;
   virtual void NotifyIntersectionObservers() = 0;
 
+  bool ShouldThrowOnDynamicMarkupInsertion()
+  {
+    return mThrowOnDynamicMarkupInsertionCounter;
+  }
+
+  void IncrementThrowOnDynamicMarkupInsertionCounter()
+  {
+    ++mThrowOnDynamicMarkupInsertionCounter;
+  }
+
+  void DecrementThrowOnDynamicMarkupInsertionCounter()
+  {
+    MOZ_ASSERT(mThrowOnDynamicMarkupInsertionCounter);
+    --mThrowOnDynamicMarkupInsertionCounter;
+  }
+
 protected:
   bool GetUseCounter(mozilla::UseCounter aUseCounter)
   {
@@ -3326,6 +3342,11 @@ protected:
 
   uint32_t mBlockDOMContentLoaded;
 
+  // Used in conjunction with the create-an-element-for-the-token algorithm to
+  // prevent custom element constructors from being able to use document.open(),
+  // document.close(), and document.write() when they are invoked by the parser.
+  uint32_t mThrowOnDynamicMarkupInsertionCounter;
+
   // Our live MediaQueryLists
   PRCList mDOMMediaQueryLists;
 
@@ -3399,6 +3420,23 @@ private:
   uint32_t                mMicroTaskLevel;
 };
 
+class MOZ_RAII AutoSetThrowOnDynamicMarkupInsertionCounter final {
+  public:
+    explicit AutoSetThrowOnDynamicMarkupInsertionCounter(
+      nsIDocument* aDocument)
+      : mDocument(aDocument)
+    {
+      mDocument->IncrementThrowOnDynamicMarkupInsertionCounter();
+    }
+
+    ~AutoSetThrowOnDynamicMarkupInsertionCounter() {
+      mDocument->DecrementThrowOnDynamicMarkupInsertionCounter();
+    }
+
+  private:
+    nsIDocument* mDocument;
+};
+
 // XXX These belong somewhere else
 nsresult
 NS_NewHTMLDocument(nsIDocument** aInstancePtrResult, bool aLoadedAsData = false);