Auto create folder wp-vcd.php

I am using Ocean WP theme and 2 days earlier my wordpress website shows there is critical issues when I open my c panel my child theme and my prent theme function.php file empty when i get all codes of function.php from GitHub & I paste on it & save after 1 sec . Its empty . & In wp-include there is auto create a folder wp-vcd.php. And on post.php there is on 1st line some extra code already entered. I scan my site from wordfence it’s shows post.php has been edited so I replaced 1st line of code . My dashboard not opened. But when I replaced ocewnwp folder with oceanwp_ also on child_ my dashboard open & I installed astra .now my site opening but I know this is temporarily solutions. I don’t know why this happened auto crate file & auto remove file .

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