Rails parses nested params incorrectly

rails_controller_params_bug_report.rb

begin
  require 'bundler/inline'
rescue LoadError => e
  $stderr.puts 'Bundler version 1.10 or later is required. Please update your Bundler'
  raise e
end

gemfile(true) do
  source 'https://rubygems.org'
  gem 'rails', github: 'rails/rails'
  gem 'byebug'
end

require 'action_controller/railtie'

class TestApp < Rails::Application
  config.root = File.dirname(__FILE__)
  config.session_store :cookie_store, key: 'cookie_store_key'
  secrets.secret_token = 'secret_token'
  secrets.secret_key_base = 'secret_key_base'

  config.logger = Logger.new($stdout)
  Rails.logger  = config.logger

  routes.draw do
    get '/' => 'test#index'
    post '/' => 'test#create'
  end
end

class TestController < ActionController::Base
  include Rails.application.routes.url_helpers

  def index
    render json: params.to_unsafe_h[:product]
  end

  def create
    render json: params.to_unsafe_h[:product]
  end
end

require 'minitest/autorun'
require 'rack/test'

class BugTest < Minitest::Test
  include Rack::Test::Methods

  def setup
    @params = {
      "items" => [
        { "brand" => { "name" => "Apple" }, "color" => "pink" },
        { "brand" => { "name" => "Samsung" }, "color" => "gold" },
      ]
    }
  end

  def test_post_params
    post '/', product: @params
    assert_equal @params, json_body
  end

  def test_get_params
    get '/', product: @params
    assert_equal @params, json_body
  end

  private

  def app
    Rails.application
  end

  def json_body
    JSON.parse(last_response.body)
  end
end

rails/rails#23997