This API call is just returning a PNG image with almost no EXIF data. In that case, the title is set by browsers to the filename, which is equal to the domain name itself. Are you seeing something else in the title? (I see fb.com)

Saw this in response headers.

Content-Disposition:"inline; filename="Facebook.png""

I am using firefox which apparently uses this header to set the title. Chrome OTOH won't do it

Interesting. I did look at headers, but missed the Content-Disposition for some reason.

Strange. I see Facebook in the title