Content Security Policy
Security is important to you. Not just to protect your own confidential information, and not just to protect your site visitors. If malware is found on your site, it will also be detrimental to your search engine rankings. Pages on which malware is discovered end up on blacklisting and are no longer indexed. It takes a lot of effort to get a page out of these blacklists.
Test your site at https://observatory.mozilla.org