I work on Concrete v 9.2.0,
I tried adding security headers in system&settings->Environment->security.
I noticed that the settings are fine the first time I check in the browser console after clearing the concrete cache, but
when pages are displayed from cache, there are no more security headers.
When pages are display without cache, I have two different rules for Stric-transport-Security and X-Frame6Options and one for Content-Security-Policy.
When pages are display with cache, I have not my values of security headers in system&settings->Environment->security.