joomla/joomla-cms — pull request #259 by KISS-Web-Design (2012-07-04 11:13:02+00:00)
Title: remove obsolete img border from tinymce.php (deprecated in html4, obsolete in html5)

When inserting an image while using tinymce the element border="0" is automatically added to the html.

eg

it is even added if you specify a border in the insert image popup

The border element was deprecated in HTML4 and is obsolete in HTML5.