I mostly (only) test in firefox, and Chrome handles this differently it seems.
I assume that's the attribution from the tile layer. In their screenshot they have an imagery layer selected, which obviously doesn't have an OSM credit. You could probably tell leaflet (or whatever map-JS you use) to show an OSM credit always to credit the POIs, although strictly speaking your existing credit in the sidebar should be sufficient.
After a loading screen crediting it, and after you've dismissed the sidebar crediting it, which is again reachable with a click. Sufficient attribution as far as I can tell.