New Post: Editor is stripping HTML

Using v2.0.12 on DNN 7.2.2
The editor is stripping HTML from my modules when opening them up for edit.

Example - HTML module on page contains this:

<ul class="list icons list-unstyled">
    <li><em class="icon icon-check"></em> Design</li>
    <li><em class="icon icon-check"></em> HTML/CSS</li>
    <li><em class="icon icon-check"></em> Javascript</li>
    <li><em class="icon icon-check"></em> Backend</li>
</ul>

and when opening in CKeditor the <em> tags and content are stripped.

Is this some plugin that's doing this? Any way to turn this off?
TIA - Marcus.