Hi BigFishWeb,
Thank you so much for your feedback!
In the meanwhile I removed a malicious script within wp-included/nav-menu.php and removed some malware, backdoor and changed PW, which solved for now the issue.
I was wondering if the html files and php files you mentioned were placed in certain folders like wp-includes, theme or plugin folders?
Hi Bigfishweb,
I have exact the same issue. My .Htaccees file is continuously overwritten with the original WordPress code and set back to permission 444 when a page of my website is visited. I checked the theme and all plugins, but still got this issue.
Did you in the meanwhile find the cause and the solutions?