Q.create() doesn't validate connectors as Q.__init__() does

[Jacob Walls]

In 98e642c69181c942d60a10ca0085d48c6b3068bb, we mitigated a SQL injection vector for user-controlled arguments to filter() and friends (CVE-2025-64459) by adding validation for the _connector argument.

We deliberately avoided adding the same validation to Q.create(), because Q.create is an undocumented internal not to be used with user-controlled input.

The Security Team then received more than one report extrapolating from CVE-2025-64459, suggesting that Q.create was missing the same validation.

Although we don't consider this a security vulnerability, we would be interested to evaluate if adding validation to Q.create to match Q.__init__ would be cheap enough to implement. A concern is how many times Q.create might be called in loops. Thus, one part of the solution here might be a refactor to reduce the number of times Q.create is called in loops in Django's code:

in contrib.contenttypes:
​https://github.com/django/django/blob/13299a6203f4bc3e5b2552c96a51ff2b15da3c43/django/contrib/contenttypes/fields.py#L682-L695
in the deletion Collector:
​https://github.com/django/django/blob/13299a6203f4bc3e5b2552c96a51ff2b15da3c43/django/db/models/deletion.py#L357-L358
...others?

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Tentatively passing over to Djangonaut Space navigators to see if a good fit for anyone (git archaeology, benchmarking, security, ORM internals)