Usage invokes insecure SSL [solved]

I know this topic was posted here earlier, and closed. But as I ran into this today, I did some more digging and found the problem. Apparently, when you modify the theme using the themes customizer some static css code is generated which will survive a url scheme change, i.e. http to https. So when you change your website’s background image for example when still using http urls. Then change to https, WordPress will still load the old http link because it did not update the absolute url to http://<domain>/wp-content/plugins/fourteen-colors/pattern-dark-inverse.svg (table wp_options, option_name theme_mods_twentyfourteen) So this is more a WordPress bug than a fourteen-colors bug. Referenced thread: https://wordpress.org/support/topic/usage-invokes-insecure-ssl?replies=4 Related bug report: https://core.trac.wordpress.org/ticket/28687#comment:23 https://wordpress.org/plugins/fourteen-colors/