iThemes Security (Solid Security) and iThemes Security Pro Won’t Protect Against Zero-Days Contrary to Their Marketing
A zero-day is a vulnerability being exploited before the developer is aware of it. One of the implications of that is that keeping software up to date won’t protect against it. So for WordPress websites, a WordPress security plugin can possibly provide protection beyond doing security basics like updating software. That is, if the plugin actually provides that type of protection. iThemes Security (which is being rebranded to Solid Security) is marketed as being just such a plugin. Here is how the developer starts marketing the plugin on the WordPress Plugin Directory (emphasis theirs):
The Best WordPress Security Plugin to Secure & Protect WordPress [Read more]