It turned out another SEVERE TOOLSET BUG which needs a very URGENT fix! It is about Toolset MODULE Manager which
1) cause MIXED CONTENT across entire web portal (apart from main domain we do have also 31(!) active sub domains in place; hosted on a dedicated server, incl. professional premium FIREWALL and certified *.wildcard SSL CERT.
This mixed content error is strictly the result of this particular MODULE MANAGER plugin's coding!
2) breaks post and page LINKS
3) BREAKS IMAGES and interferes displaying images properly
4) Interferes DNS/CLOUD PROXY Firewall
5) breaks SSL entirely by marks a proper WordPress setup INSECURE
6) slows down server performance drastically
7) several minor issues ...
When discovered several teams tried a work around which is because of the mixed content caused by MODULE MANAGER coding (the image link is hardcoded in the plugin files) by override this through adding the following line to the site .htaccess file:
Header set Strict-Transport-Security "max-age=31536000" env=HTTPS
BUT this is impossible too.
The mixed content error does not only appears and impact our web portal at the backend, it also alters functionality (see above as listed), so our customer and users are confronted with that issue as well.
Originally this SEVERE problem was discovered by the WPMU DEV Team (and it is confirmed by FIVE independent server specialist such as server provider 1&1, two PLESK Teams one based in USA the other one in EUROPE, SUCURI Firewall provider, and as already mentioned discovered from the WPMU DEV Team.
Please provide immediate solution by rewriting the code of MODULE MANAGER!
Regards
Beate