Hey @brisch,
Wordfence protects against a wide variety of attacks. Whether you were hacked because of an unknown attack method or because there is some other issue in your system is hard to say. Some plugins contain vulnerabilities that are so bad that Wordfence can’t protect against them. The same goes for servers.
Regarding how they gained entry, here are some possible scenarios:
Are there other sites hosted on the same hosting account? If so, they could have been infected and spread the infection to this site.
You may be using a plugin or theme with a vulnerability that is so severe that we cannot protect against it.
Your wp-config.php file is readable to the hacker, either directly via your account, via a vulnerable plugin or another hacked site on the same server.
The hosting accounts on the server are not adequately isolated on the server, so the hacker has access to your database via another user’s database.
The server software has vulnerabilities that allow the hacker to get root access
You were actually hacked many months ago, but the backdoor was not activated until now.
Here’s a guide that may help you clean the site. However, if you’re not comfortable with this or the site becomes reinfected I’d suggest reaching out to a professional hack repair service to have the site professionally cleaned and patched.
https://www.wordfence.com/docs/how-to-clean-a-hacked-wordpress-site-using-wordfence/
Thanks,
Gerroald