Alex,
I do believe the issue lies within TinyMCE. I see the script tags are removed before you even post the field.
To recreate this, open up a static page, and in the content textarea, attempt to place <script> </script> using the source code editor.
Then hit OK and then reopen the source code window. <script> tags are gone.
Quick research shows that we need to add this to tinymce.init function:
Code:
cleanup: false,
verify_html: false,