I've succesfully managed implementing custom attributes creating upcasts and downcasts converters; all seems to work but I'm now blocked on how to get the actual data back from the editor; if I use:
editor.getData()
I got the html tag (an <img> one) without the custom attributes while in the CKEditor Inspector I can see the attributes in both the model and the view.
How I can retrieve the data with the custom attributes?