The wifi was blocking certain sites, using a device or software which generated a certificate on the fly to generate a message (if I chose to click through the error).

I think that this is a factual, mappable scenario but did not see anything under https://taginfo.openstreetmap.org/search?q=internet_access%3A that looked relevant. A ‘hostile network’ is a more or less standard term.

I also asked in slack.openstreetmap.us but nobody suggested anything.