digitalchild on "[Plugin: Wordfence Security] Fatal error: Unknown: Failed opening required"

I have had the same issue on a client site, though it was only affecting /wp-admin. The issue also started 2 or 3 days ago, but is not related to any updates or changes in the firewall AFAIK, since the client has restricted permissions— unless there was an auto-update.

I was also able to fix it using the solution @ET linked to. I'm posting it below for future searchers (to save scrolling through to the comment with the fix):

1. Look for a file in your root WordPress directory (the one with wp-config.php) named .user.ini Now, either:

2a. rename, or backup and delete that file or

2b. edit the file and either comment out or delete the lines:

; Wordfence WAF
auto_prepend_file = '/home/dezi3014/public_html/wordfence-waf.php'
; END Wordfence WAF

If that doesn't work, look for those same lines in .htaccess and php.ini (location of the latter will vary from server to server)

All that said, it would be nice to know what is actually causing the error, since the call is to a file that actually *does* exist. Knowing the problem will help me know how to prevent it from happening again.