Suggestion: It would be nice to have full control over ActionDispatch parameter filtering
I needed to filter a "data" parameter for one of my controllers, but this is a very generic word, so I didn't really want to filter every instance of this key for all of my controllers.
The current implementation of "config.filter_parameters" was not flexible enough for me to write this kind of custom logic. So I wrote a monkey patch for 'action_dispatch/http/parameter_filter', and added the concept of CustomFilter classes (name needs some work.) My idea is that you can create a subclass from ActionDispatch::Http::ParameterFilter::CustomFilter, and then write a custom filter method that receives the params Hash, and returns a filtered hash.
I use this to look at the "controller" and "action" keys, so I can set up different filtering for different controllers.