Hi @peakdistrictwalks,
Thanks for reaching out to us.
This sounds like it could be the Japanese keyword hack: https://web.dev/fixing-the-japanese-keyword-hack/
We have a video (43:17) and article that describe this specific type of hack: https://www.wordfence.com/blog/2020/09/the-hacker-motive-what-attackers-are-doing-with-your-hacked-site/
You can clean the site by using the following guide: https://www.wordfence.com/docs/how-to-clean-a-hacked-wordpress-site-using-wordfence/
Make sure and get all your plugins and themes updated and update WordPress core, too. As a rule, any time I think someone’s site has been compromised, I also tell them to update their passwords for their hosting control panel, FTP, WordPress admin users, and database. Make sure to do this because attack vectors around your hosting or database environments are outside of Wordfence’s influence as an endpoint firewall.
Additionally, you might find the WordPress Malware Removal section in our Learning Center helpful: https://wordfence.com/learn/
If you’re unable to clean this on your own, there are paid services that will do it for you. Wordfence offers one and there are others. Regardless, if you choose to clean it yourself or let someone else do so, we recommend that you make a full backup of the site beforehand.
Thanks,
Tiffany