Any developer who uses a CMS with a wysiwyg text editor knows the frustrations of clients pasting content from MS Word and other word processing programs directly into the editor, complete with unwanted styles, and even markup elements, causing all sorts of problems on our otherwise perfectly-formatted pages.

Mura CMS uses the ubiquitous CKeditor (formerly FCK) with a number of features enabled by default, including a "Paste as Plain Text" button. If clients remembered to use this, we would be all set. But, they don't.

Fortunately, there's an easy one-line fix.
Just open up [siteid]\includes\themes\[theme]\js\editor\styles.js

and paste in this line

CKEDITOR.config.forcePasteAsPlainText = true;

That's it. All pasting of content should now be clean, with extra styles and markup removed, just as if you had clicked "paste as plain text" in the editor toolbar.