<img> Tags are rendered with border attribute in HTML5 mode
By default <img> Tags are rendered with a border attribute in HTML5. Only with XHTML they are omitted.
This is a bug. in HTML5 the border attribute is not allowed.
You can disable the border attribute by using config.disableImgBorderAttr = 1, but it should be disabled by default when using html5 to produce valid code.
(issue imported from #M16740)