MongoDB Mongoid: code injection

Mongoid does not neutralize a string-typed query criterion supplied to its query builder, and instead passes it to the database as a server-side JavaScript expression. An unauthenticated party able to influence the value an application supplies as a query argument may cause code of their choosing to be evaluated by the database engine. This may result in unintended disclosure of stored field values, unintended selection of documents for application-initiated writes, and reduced database performance.