We acknowledge the issue and are working on this to fix it.

Is there a codebase somewhere for petscan? Perhaps if it is the only use case then we could avoid returning Javascript from the server side

In T347317#9198582, @isarantopoulos wrote:

Is there a codebase somewhere for petscan?

https://github.com/magnusmanske/petscan_rs/

In T347317#9198582, @isarantopoulos wrote:

Is there a codebase somewhere for petscan? Perhaps if it is the only use case then we could avoid returning Javascript from the server side

I think thats https://github.com/magnusmanske/petscan_rs/

Thanks for pointing that out!
I have added to the existing issue https://github.com/magnusmanske/petscan_rs/issues/141
The issue is that the new ores-legacy service that has been in place to assist in the ORES to Lift Wing migration (https://wikitech.wikimedia.org/wiki/ORES) does not accept JSONP callbacks and users should work with making GET requests (in this case using https://ores.wikimedia.org/v3/scores/).
I think best thing would be to replace this function call with a fetch method that performs a GET request.