Comment by zygentoma

Well, you get the warning, but as long as HSTS is not active, you can still click on "Accept the risk and continue" …

[EDIT:] Just checked a bit closer, they are using an LetsEncrypt cert for "cuii.telefonica.de", which is obviously the wrong domain, but as I said above, as long as HSTS is not active for "annas-archive.li", you can still bypass via the button.