The mapframe attribution (kartographer-attribution) is:
"Wikimedia maps | Map data © OpenStreetMap contributors"
There is also kartographer-attribution-short, which is similar but shorter.
However, the maps.wikimedia.org one is:
"Map data © OpenStreetMap contributors"
https://maps.wikimedia.org/osm-intl/info.json is the same (though they are separate until https://github.com/kartotherian/server/pull/5 is merged).
The last two don't mention or link to the Wikimedia Terms of Use.
In fact, https://maps.wikimedia.org doesn't mention Wikimedia anywhere, other than the <title>.
See also T187288: maps.wikimedia.org copyright attribution should be translated.