Optimizely Search & Navigation includes public properties on an object when indexing it by default. The simplest way to exclude a property is to annotate it with the JsonIgnore attribute in the Newtonsoft.Json namespace.

Example

using Newtonsoft.Json;

public class User {
  public string Username {
    get;
    set;
  }

  [JsonIgnore]
  public string Password {
    get;
    set;
  }
}

You can also exclude properties or other previously included fields by customizing the client conventions.

//using EPiServer.Find.ClientConventions;

client.Conventions
  .ForInstancesOf<User>()
  .ExcludeField(x => x.Password);

The above code excludes the Password property from instances of the User class and instances of classes that inherit the User class.