XF 2.0 Edit a custom user field from a widget at home page (possibly through ajax)

[abdfahim]

I am planning to make a Widget where the visitor can update a particular custom user field. It'd be even better if I can do it without refreshing the whole page (i.e. through ajax).

However, I am not finding any resource from where I know where to begin. Any link/addon/guide/template which has a similar functionality so that I can inspect the code, please?