diff -up webkitgtk-2.20.3/Source/WebCore/accessibility/AccessibilityObject.cpp.atk_crash webkitgtk-2.20.3/Source/WebCore/accessibility/AccessibilityObject.cpp
--- webkitgtk-2.20.3/Source/WebCore/accessibility/AccessibilityObject.cpp.atk_crash	2018-04-09 14:00:57.000000000 +0200
+++ webkitgtk-2.20.3/Source/WebCore/accessibility/AccessibilityObject.cpp	2018-07-24 13:40:41.183634369 +0200
@@ -67,6 +67,7 @@
 #include "RenderView.h"
 #include "RenderWidget.h"
 #include "RenderedPosition.h"
+#include "ScriptDisallowedScope.h"
 #include "Settings.h"
 #include "TextCheckerClient.h"
 #include "TextCheckingHelper.h"
@@ -1771,7 +1772,11 @@ void AccessibilityObject::updateBackingS
     // Updating the layout may delete this object.
     RefPtr<AccessibilityObject> protectedThis(this);
     if (auto* document = this->document()) {
-        if (!document->view()->layoutContext().isInRenderTreeLayout() && !document->inRenderTreeUpdate() && !document->inStyleRecalc())
+        if (!document->view()->layoutContext().isInRenderTreeLayout()
+            && !document->inRenderTreeUpdate()
+            && !document->inStyleRecalc()
+            && ScriptDisallowedScope::InMainThread::isScriptAllowed())
+
             document->updateLayoutIgnorePendingStylesheets();
     }
     updateChildrenIfNecessary();