Ruby

HSTS in Rails is one of those security wins that looks trivial right up until you break a domain for months. If you run a Rails app over HTTPS, you should probably send Strict-Transport-Security. But the real question for a developer team isn’t “should we use HSTS?” It’s “which HSTS policy should we ship, and how safely can we get there?” Rails makes this pretty easy, but the tradeoffs matter. A weak HSTS policy leaves downgrade risk on the table. An aggressive one can lock users and subdomains into HTTPS before your infrastructure is ready. ...

HSTS on Heroku looks simple right up until you ship it wrong and lock users into a bad HTTPS setup. I’ve seen this happen a few times: someone enables SSL on Heroku, adds a redirect to HTTPS, throws in Strict-Transport-Security, and calls it done. Then a week later they realize staging is broken, a custom domain is misconfigured, or preload was enabled before every subdomain was actually ready. Heroku makes TLS termination easy. That does not mean HSTS is automatic, or safe by default. ...