js/tinymce/wp-tinymce.php 403'ing

This is annoying – after upgrading to v4, wp-includes/js/tinymce/wp-tinymce.php is 403’ing

I’ve:

• reuploaded /wp-includes/ and /wp-admin/
• deactivated all plugins
• deactivated all themes
• turned on wp_debug, and error_reporting()
• checked error log – nothing
• changed all .htaccess‘s to just the wp-generated rewrites
• changed the content of wp-tinymce.php to just a hello world, same 403
• changed the chmod of the file, and each of it’s parents to 777, still a 403

Now I’m completely out of options. I’m starting to think something in apache thinks there’s an inject or some crap like that. I’ve contact host, I’m looking for ideas, please advise!

(For keyphrases for anyone else searching this problem: tinymce not working, text formatting not working, visual tab not working, text all white no buttons wordpress editor.)