Ash.count, Ash.exists and Ash.aggregate skip related resources' read policies in filters and sorts

Incorrect Authorization vulnerability in ash-project ash allows an actor to infer data in related records they cannot read via Ash.count/2, Ash.exists/2 and Ash.aggregate/3.

Ash.Actions.Aggregate.run/4 (lib/ash/actions/aggregate.ex) applied only the root resource's read policy before running the aggregate query. The read path also applies each related resource's read policy to filter and sort references that cross a relationship, directly (for example comments.body) or through an aggregate over one, but the aggregate path skipped that step. A caller whose filter or sort reaches these functions, for example through Ash.Query.filter_input/2, an ash_lua script, or an AshAi tool offering count or exists results, can test conditions against related rows hidden from them and recover their existence and attribute values one query at a time. Ash.read/2 and its page counts are not affected.

This issue affects ash: from 2.6.0 before 3.34.6.

Reachable only when an application passes caller-supplied filters or sorts that cross a relationship into Ash.count/2, Ash.exists/2 or Ash.aggregate/3 (directly, through ash_lua read operations, or through AshAi count, exists or aggregate result types), and a related resource's read policy is stricter than the root resource's.