How to fix xenforo text editor after upgrading to a newer version
If the xenforo text editor looks like that after upgrading to a newer version, you should know that they changed the style and the images.
The problem is that the style have been changed but the image for the text editor buttons from YOUR THEME is still to an older version.
Copy from the upgrade folder these files to your theme:
styles\my-style\xenforo\xenforo-ui-sprite.png styles\my-style\xenforo\magnifier.png styles\my-style\xenforo\editor\icons.png styles\my-style\xenforo\widgets\style-preview.png styles\my-style\xenforo\permissions\edit.png