Comment by robertlagrant a day ago
> This case highlights an interesting tension in web security: the balance between protection and usability.
This isn't a tension. This rule should not be applied at the WAF level. It doesn't know that this field is safe from $whatever injection attacks. But the substack backend does. Remove the rule from the WAF (and add it to the backend, where it belongs) and you are just as secure and much more usable. No tension.
I don't agree. WAFs usually add more attack surface than they remove.
https://www.macchaffee.com/blog/2023/wafs/
Of course, Wordpress is basically undefendable, so I'd never ever host it on a machine that has anything else of value (including e.g. db credentials that give access to much more than the public content on the WP installation).
Again, there is no tension.
People will manage to circumvent the firewall if they want to attack your site. But you will still pay, and get both the DoS vulnerabilities created by the firewall and the new attack vectors in the firewall itself.
I would say it’s a decent security practice to apply WAF as a blanket rule to all endpoints and then remove it selectively when issues like this occur. It’s much, much, harder to evaluate every single public facing endpoint especially when hosting third party software like Wordpress with plugins.