Rails has quite a few security related configurations. One of which relates to enforcing mass assignment protection.
<%= %q{
config.active_record.whitelist_attributes=false
} %>
This configuration forces an application developer to whitelist attributes that can be modified with mass-assignment. When this configuration is set to false any attribute can be mass-assigned.
<%= %q{
config.active_record.whitelist_attributes=true
} %>
Once this configuration is updated to true and the application is restarted, any attributes to be mass-assigned will have to be defined as attr_accessible.