Does anybody know of a way to set a HTTP response header only if it is missing from the initial created response (proxied response via mod_jk) in Apache HTTP 2.4.6? I'm looking for a way to set the X-FRAME-OPTIONS header but only if the source page has not explicitly set it.
I know Apache HTTP 2.4 has the setifempty action from mod_header but that doesn't exist until Apache HTTP 2.4.7. I don't want to change the apache version because then it would take me out of my distribution's (CentOS 7) update path.
