New paragraph attributes copy

Hello,

I'd like to trace changes made by a user editing some text. I have for example this original paragraph loaded by a code in a editor:

<p original="true">text</p>

When user press enter key (in WYSIWYG mode of course) and write "any new text", the source code is changed to:

<p original="true">text</p>
<p original="true">any new text</p>

How can I avoid to copy the attribute "original"?
I was already searched this forum, but without any success :(

I use 2.4.3 built 15657 version.

Thanks a lot

Jirka