CSRF not working in Rails?

If I create a brand new Rails application (using Rails 3.0.9) and knock up a quick bit of scaffolding as follows:

$ rails new testing
$ rails g scaffold thing name:string

Then app/controllers/application_controller.rb contains a "protect_from_forgery" by default, so it should check the authenticity_token during a POST create. At least, that's my understanding.

Why then, does this line successfully create a new Thing, without supplying the token.

$ curl -F "thing[name]=abc123" http://localhost:3000/things

The log entry says:

Started POST "/things" for 127.0.0.1 at 2011-07-05 08:29:18 +0100
  Processing by ThingsController#create as 
  Parameters: {"thing"=>{"name"=>"abc123"}}
  AREL (0.3ms)  INSERT INTO "things" ("name", "created_at", "updated_at") VALUES  ('abc123', '2011-07-05 07:29:18.484457', '2011-07-05 07:29:18.484457')
Redirected to http://localhost:3000/things/18
Completed 302 Found in 89ms

I can also do this to delete records:

$ curl -X DELETE http://localhost:3000/things/18

The same thing happens in production mode. Doesn't t开发者_如何学运维his leave my application open to CSRF?

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If you pass invalid CSRF token or send request without it, Rails will nullify session, so protect_form_forgery is useless if your application could be accessed by everyone. But it will save your application from CSRF attack if you have session-based authentication system.

More info: How does Rails CSRF protection work?