Affected: ormar-orm ormar

ormar is a async mini ORM for Python. Versions 0.23.0 and below are vulnerable to Pydantic validation bypass through the model constructor, allowing any unauthenticated user to skip all field validation by injecting "__pk_only__": true into a JSON request body. By injecting "__pk_only__": true into a JSON request body, an unauthenticated attacker can skip all field validation and persist unvalidated data directly to the database. A secondary __excluded__ parameter injection uses the same pattern to selectively nullify arbitrary model fields (e.g., email or role) during construction. This affects ormar's canonical FastAPI integration pattern recommended in its official documentation, enabling privilege escalation, data integrity violations, and business logic bypass in any application using ormar.Model directly as a request body parameter. This issue has been fixed in version 0.23.1.

Affected: PyPI: ormar

### Summary

A Pydantic validation bypass in `ormar`'s model constructor allows any unauthenticated user to skip **all** field validation — type checks, constraints, `@field_validator`/`@model_validator` decorators, choices enforcement, and required-field checks — by injecting `"__pk_only__": true` into a JSON request body. The unvalidated data is subsequently persisted to the database. This affects the **canonical usage pattern** recommended in ormar's official documentation and examples.

A secondary `__excluded__` parameter injection uses the same design pattern to selectively nullify arbitrary model fields during construction.

### Details

**Root cause:** `NewBaseModel.__init__` ([`ormar/models/newbasemodel.py`, line 128](https://github.com/collerek/ormar/blob/master/ormar/models/newbasemodel.py#L128)) pops `__pk_only__` directly from user-supplied `**kwargs` before any validation occurs:

```python # ormar/models/newbasemodel.py, lines 128-142 pk_only = kwargs.pop("__pk_only__", False) # ← extracted from user kwargs object.__setattr__(self, "__pk_only__", pk_only)

new_kwargs, through_tmp_dict = self._process_kwargs(kwargs)

if not pk_only: # Normal path: full Pydantic validation new_kwargs = self.serialize_nested_models_json_fields(new_kwargs) self.__pydantic_validator__.validate_python( new_kwargs, self_instance=self ) else: # Bypass path: NO validation at all fields_set = {self.ormar_config.pkname} values = new_kwargs obj…