Text pasted in CKEditor isn't clean On a Drupal 8 installation, with CKEditor enabled for Full HTML format, when I paste text from Word with cmd+V, the source code includes format that makes the code dirty.

Example: 

&lt;p&gt;&lt;span style="font-size:12pt"&gt;&lt;span style="line-height:115%"&gt;&lt;span style="font-family:Helvetica"&gt;Lorem ipsum dolor.&lt;/span&gt;&lt;/span&gt;&lt;/span&gt;&lt;/p&gt;


How can I force it to clean the code from Word?
For reference, there was a backwards-compatibility break in CKEditor v4.6 - it removed some of its own paste-from-Word button's cleaning. See this discussion on the Drupal side: https://www.drupal.org/project/drupal/issues/2871539

Note comment #6 there offers another workaround - responding to the 
afterPasteFromWord CKEditor event in some custom Javascript and filtering exactly as desired.