Tinymce editor is not striping HTML code in laravel 5 - laravel

Question

I am making a blogging application in laravel 5. I am using tinymce for writing post. My application is working for adding new post. But when I am updating posts(which contains html and java script code), then tinymce is not striping html and java script tags.
For example, my post is:
<script>alert("hello");</script>
<h3>heading 3 </h3>
italic text for test
bold and italic for test
Note:
My third line is italic and fourth line is italic and bold. I don't know how to decorate text here on stackoverflow.
Above written code should be stripped and should display as it is.
It is displaying well in browser. When I try to edit this post then I get in tinymce editor
heading 3
italic text for test
bold and italic for test
I want to strip these tags in tinymce editor.
UPDATE:
I am using tinymce by adding this code
<script type="text/javascript" src="{{ asset('/js/tinymce/tinymce.min.js') }}"></script>
<script type="text/javascript">
tinymce.init({
selector : "textarea",
plugins : ["advlist autolink lists link image charmap print preview anchor", "searchreplace visualblocks code fullscreen", "insertdatetime media table contextmenu paste"],
toolbar : "insertfile undo redo | styleselect | bold italic | alignleft aligncenter alignright alignjustify | bullist numlist outdent indent | link image"
});
</script>
If you still can not understand the question. I embed code in by blog post in tinyMCE which is stripped in browser. When I edit the post then code is not stripped in tinyMCE.
Live demo of this problem is at sweet-blog.herokuapp.com