Mathesar: Missing collaborator checks allowed access to saved explorations in other databases

Summary

Mathesar is a web application that makes working with PostgreSQL databases both simple and powerful. From 0.2.0 to before 0.10.0, explorations.get, explorations.replace, and explorations.delete operate on an exploration_id without verifying that the requesting user was a collaborator on the exploration’s database. An authenticated user on the same Mathesar installation who knew or guessed an exploration ID could read, replace, or delete a saved exploration belonging to a database where they were not a collaborator. This affected Mathesar-managed saved exploration definitions, including names, descriptions, selected columns, display metadata, filters, sorting, and transformations. This vulnerability is fixed in 0.10.0.