Power CMS not saving all of the tag Information

I have a site from which I am adding content to PowerCMS
I am finding that some CSS information is not saved on editing.

Here is an example.

If I add the following content to PowerCMS via Webassist->CMS->Add Content to PowerCMS, it is saved correctly.

<figure class="pad_bot1"><img src="/images/swavesey_bg.png" alt="" /></figure>
<p>Swavesey Village College has been delivering the Introduction to Construction BTEC to 14-16 year olds since 2007.</p>

If I subsequently edit the content in PowerCMS, either in admin or inline, I get the following...

<img alt="" src="/images/swavesey_bg.png" />
<p>Swavesey Village College has been delivering the Introduction to Construction BTEC to 14-16 year olds since 2007.</p>

The <figure> tag is ignored completely

in v4, CKEditor have introduced an advanced content filter which removes unrecognized tags, see this page for details:
http://docs.ckeditor.com/#!/guide/dev_advanced_content_filter

to prevent the tag from being removed, in the webassist/plugins/ckeditor/config.js file, change:

config.enterMode = CKEDITOR.ENTER_BR;

to:
config.enterMode = CKEDITOR.ENTER_BR;
config.allowedContent=true;