Mongoose is a MongoDB object modeling tool designed to work in an asynchronous environment. Prior to 6.13.12, 7.8.13, 8.24.7, and 9.11.4, Mongoose uses attacker-controlled discriminator key values, including the default __t field, to index plain-object registries such as Model.discriminators and schema.discriminators without requiring an own property. Values such as constructor, toString, or hasOwnProperty can therefore resolve to inherited built-in functions instead of a registered discriminator, causing type confusion in model construction, document creation, hydration, query and update casting, embedded discriminators, and populate operations. In the bulkWrite() insertOne path with skipVa