I take all reports of security issues very seriously. Looking further into this right now away.
My initial educated guess, based on the evidence you have provided, was that there is possibly a link somewhere that I missed in updating last December and / or Chrome has updated and / or one or more certificates have expired. Analysis suggests the latter two; our certificates have limited life and some have expired. I have just renewed a couple of the key ones - see if that works for the message (it will probably not fix the unread topics not being properly reported)
I am
not worried, but I am very interested. Whilst we look to make all transactions though https these days, it's still less than 6 months we've being doing so and - you may recall - the main reason we did so was as a re-assurance; the Coffee Shop does not collect payments or personal data which needed that extra layer. Still worth having the layer but no panic needed.
I will be very interested in feedback from other members to help me analyse and gain more evidence - either a pattern of problems or a deathening silence which would suggest it's cured or a very specific issue.