Enabled script/style tags support in TinyMCE 6

js/mage/adminhtml/wysiwyg/tinymce/setup.js

@@ -70,6 +70,11 @@ tinyMceWysiwygSetup.prototype =
         var settings = {
             selector: this.selector,
             config: this.config,
+            valid_children: '+body[style]',
+            custom_elements:"style,~style",
+            protect: [
+                /([\S]?)<script([\s\S]*?)>([\S]*?)<\/script([\s]*?)>([\S]?)/ig
+            ],
             menu: {
                 insert: {
                     title: 'Insert',