Mass-assignment protection

In the computing world, where software frameworks make life of developer easier, there are problems associated with it which the developer does not intend. Software frameworks use Object Relational Mapping (ORM) tool or Active Record Pattern for converting data of different types and if the software framework does not have a strong mechanism to protect the fields of a class (the types of data), then it becomes easily exploitable by the attackers. These frameworks allow developers to bind parameters with HTTP and manipulate the data externally. The HTTP request that is generated carries the parameters that is used to create or manipulate objects in the application program. 
The phrase mass assignment refers to assigning values to multiple attributes in a single go. It is a feature available in frameworks like Ruby on Rails that allows the modifications of multiple object attributes at once using modified URL. For example, 
 @person = Person.new(params[:person]) #params contains multiple fields like name, email, isAdmin and contact
This Mass Assignment saves substantial amount of work for developers as they need not set each value individually.
Threats.
In Mass Assignment, a malicious agent can attack and manipulate the data in various ways. It can send the tags which can make him assign various permissions which would otherwise be forbidden. For example, a database schema has a table "users" having field "admin" which specifies if corresponding user is admin or not. Malicious agent can easily send the value for this field to the server through HTTP request and mark himself as an admin. This is called Mass assignment vulnerability. It explores the security breaches that can be done using mass assignment.
 Github got hacked in 2012 by exploiting mass assignment feature. Homakov who attacked the Github gained private access to Rails by replacing his SSH with SSH key of one of the members of Rails github.
Protection methods.
We can perform some changes in the active record models to ensure the protection of our data.
Class Person < ActiveRecord::Base
 has_many :projects
 attr_protected :assign_project
end
This method optionally takes a role option using :as which enables to define multiple mass-assignment groupings. These attributes will have the :default role in case no role role is assigned. Here is an example which illustrates that assign_project will only be visible to admin. 
attr_protected :assign_project, :as => :admin
attr_accessible :name, :email, :contact 
Sometimes developer might forget adding attributes as accessible. So as to avoid this, recent versions of Rail has config setting codice_5" which creates blank white list of attributes and protects from Mass Assignment Vulnerability. Models still need to explicitly whitelist or blacklist accessible parameters.