Inconsistancy when using widget macro to play video on Youtube with HTTPS URL

Hello,

After created a page by using the widget macro with this URL: https://www.youtube.com/embed/_f4CXRo8Sqs, we explore the source code of the page:

<div id="content-editable-container" class="wiki-content">
     <p>
       <iframe class="youtube-player" type="text/html" style="width: 400px; height: 300px" src="http://www.youtube.com/embed/_f4CXRo8Sqs" frameborder="0">
       </iframe>
     </p>
</div>

It looks like even we force the URL to HTTPS, the widget macro transfer automatically HTTPS to HTTP. Both of them is working but it cause a security issue on the customer side.

Thanks in advance for your help.