Clickjacking is especially scary because most web apps are probably vulnerable. The default httpd.conf that ships with most package managers doesn't include the X-Frame-Options header. (Perhaps it should.)
Based on my testing, it appears Rails does not add that header either. Do any other frameworks?
It appears we're each partially right: If you generated a new Rails app after August 2012, you get the header by default. If you generated the app before August 2012, you do not get the header by default.
So PSA: Updating Rails in an existing app does not cause this header to be added. You must add it yourself in application.rb if it's not already there. See garethadams' footnote #2 above.
Most frameworks/servers don't do that. It's bad design of web specs, not a bug actually. Developers don't have to remember about it... And yeah, I added default_headers to Rails a while ago.
Based on my testing, it appears Rails does not add that header either. Do any other frameworks?