I’ve found a solution!
Inserting the <code></code>
tags around the [WolframCDF source= .... ]
statement seems to solve the problem.
Add them in the text mode of the editor (and not in visual mode). In the text editor you’ll so change the WolframCDF call from something like:
[WolframCDF source="https://www.lucamoroni.net/wp-content/uploads/2014/11/WaveMotion.cdf"
width="939" height="1014"
altimage="https://www.lucamoroni.net/wp-content/uploads/2014/11/WaveMotion.png"
altimagewidth="939" altimageheight="1014"]
to someting like:
<code>[WolframCDF source="https://www.lucamoroni.net/wp-content/uploads/2014/11/WaveMotion.cdf"
width="939" height="1014"
altimage="https://www.lucamoroni.net/wp-content/uploads/2014/11/WaveMotion.png"
altimagewidth="939" altimageheight="1014"]
</code>
Thanks to Pickett for the trick (in this thread) and to Nicole Ehrlich (in this thread)