on this map I see hundreds of other routes named in Russian

Michal, not hacked. The folks at OSM are referring to it as vandalism. Apparently it's been going on for a while and while it's a PITA I don't think (at this stage anyway) that it's anything to concern the users of CT. The OSM community see it differently, naturally ebough.

I'd imagine (total amateur guess here) that the monthly updates from OSM provide a certain amount of insulation for CT.

More info here if you want it.

https://community.openstreetmap.org/t/have-you-spotted-vandalism-on-openstreetmap-org/114684

They do indeed and I’m not planning to take an update while this is going on.

(Just to clarify, the CyclOSM layer is a third-party layer and not one provided by cycle.travel itself!)

Since you are using OSM layer, it strikes your image, you should be concerned that your supplier does not meet the requirements

It’s an optional layer and it’s not a “supplier” as there’s no money changing hands. The main cycle.travel mapping is unaffected.

I happen to use only this layer, so I will have to look for something else

Wanted to report the same. That's a pity, as the CycleOSM layer is the best one for me. It combines designated cycling-routes with a nice view upon the landscape to be able to plan beautiful routes.

that's frustrating.