Content Security Policy (CSP) definition in Cybersecurity

Content Security Policy is a computer security standard introduced to prevent cross-site scripting (XSS), clickjacking and other code injection attacks resulting from execution of malicious content in the trusted web page context.

Open source or Free solutions

1. ModSecurity (with Apache or Nginx)
2. Secure Headers for Ruby on Rails

Paying solutions

1. Cloudflare
2. Qualys