iframe content vanishes for non admins

Hi there – thank you for this great plugin!
For me as an admin it works toally fine. We use
[iframe <script type='text/javascript' src='https://xxx'></script><iframe seamless frameborder=0 allowfullscreen webkitallowfullscreen mozallowfullscreen src='https://xxx' width='640' height='360'></iframe> ]
This works for me, however our authors, who also use the shortcode, are not able to use the iframe. When they save the page, all the content between [iframe ] gets deleted. Is there some setup we’d have to do for making authors able to insert iframe shortcodes?
Thank you in advance!