Potential SQL injection via _connector keyword argument in QuerySet and Q objects

An issue was discovered in 5.1 before 5.1.14, 4.2 before 4.2.26, and 5.2 before 5.2.8. The methods `QuerySet.filter()`, `QuerySet.exclude()`, and `QuerySet.get()`, and the class `Q()`, are subject to SQL injection when using a suitably crafted dictionary, with dictionary expansion, as the `_connector` argument. Earlier, unsupported Django series (such as 5.0.x, 4.1.x, and 3.2.x) were not evaluated and may also be affected. Django would like to thank cyberstan for reporting this issue.