This question already has an answer here:
Recently I've noticed that whenever I open a question that has
imgur.com-linked images, I get a mixed content warning (and, indeed, imgur links have
http: prefix), which is strange since I use HTTPS Everywhere extension for Firefox (which should set all prefixes to
https). That also seems to be true for some other sites (which might suggest that it's a Firefox problem).
EDIT: whatever the site configuration, I expect HTTPS Everywhere to replace the imgur-links with their https versions (they do work on their own). Moreover the extension has a ruleset specifically for that site. Isn't it correct and shouldn't that be enough?