Why help.libreoffice.org produces an "invalid certificate" error?

If using https://help.libreoffice.org in Internet Explorer then I get Certificate Error. Why do I get this error? It looks like help.libreoffice.org is using the same certificate as www.documentfoundation.org. Can administrators fix this problem? Where can I report this “bug”? Probably not on LibreOffice bug tracker isn’t it?

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I think bug tracker is pretty good place to report it, under component WWW.

https://www.libreoffice.org/bugzilla/enter_bug.cgi?product=LibreOffice&component=WWW

BTW, Firefox and Chrome don’t mind this at all.