Strange code injected in Tinymce when switching to visual and back to text mode

I have a test page with 5 png social icon images. When I switch to visual mode and back to text mode a code is injected into the img tag. However, it happens only on 4 of the images.

Also strange is the 4 images with the injection are invisible on the test page and invisible in the media library even though the images are there and confirmed with the file manager in c-panel. Can images be infected?

img class="alignleft vzkuanmjbiglbfyvktdb"

If I take out alignleft, I still get:
class="vzkuanmjbiglbfyvktdb"

After WP update to 4.2.2:
latnjwdpkwqdvtkahcgm

Any ideas on what is going on?