The Design Decisions
But this is not true for <script> and </script> tags and all the code associated with them. If you edit and then save or update either a post or page in Visual Edit then WordPress will thoughtfully strip out, erase and otherwise eradicate all those <script>…</script> tags and associated code for you. The only way to recover it is to go back to the last Revision[make sure you have Revisions checked on in the WordPress screen options at the top upper right of the page or post editor or otherwise the Revisions option will be hidden] grab the code. and then restore in the safe confines of the HTML editor.