Looks like I have the same problem. I was able to localize it to ACF plugin. Didn’t find fix yet.
also check folder permissions. it solved my problem.
i’ve solved the issue installing Sucuri plugin and “hardening” directories wp-content and wp-includes.
the same here. still looking for code to clean
the page is here: http://labs.sucuri.net/signatures/malware-entry-mwjsgen2
did you manage to clean up your website?
