I mistakenly changed the /var/www/html/index.html

I mistakenly changed the /var/www/html/index.html and it’s affecting all sites.
How do I get this file back as upgrade couldn’t fix the problem.

Please help!

Welcome @JosephChuksT Happy you are here

Cyberpanel does not serve any files here. All website files are served at /home/mydomain.com/public_html and all child domain websites can be served in any folder at /home/mydomain.com/

Thanks Joe, I got the problem fixed by by VPS provider.