In Django (and Python in general) you have a form abstraction that validates the user input and filters out unwanted fields, preventing problems like this. On Rails (and Ruby in general) they don't use such abstraction (I do myself, using an implementation of forms abstractions[1] very similar to what Django provides).
Instead they send the params dictionary (which contains url captures, POST and GET values) directly to the model instance, and expect the model to deal with it. The problem with this approach is that it gives too much responsability to the model. Other than forms not necessarily mapping directly to models, making this more complicated, it is also prone to security issues, like the one Github suffered. ActiveRecord (Rails ORM) allows you to whitelist and blacklist fields at the model level (which IMO is the wrong way to do this, Django got it right), but a lot of people don't do it.