GHSA-hg9m-67mm-7pg3

# Summary `{field}.isFilterable` access control can be bypassed in `update` and `delete` mutations by adding additional unique filters. These filters can be used as an oracle to probe the existence or value of otherwise unreadable fields.

Specifically, when a mutation includes a `where` clause with multiple unique filters (e.g. `id` and `email`), Keystone will attempt to match records even if filtering by the latter fields would normally be rejected by `field.isFilterable` or `list.defaultIsFilterable`. This can allow malicious actors to infer the presence of a particular field value when a filter is successful in returning a result.

# Impact This affects any project relying on the default or dynamic `isFilterable` behaviour (at the list or field level) to prevent external users from using the filtering of fields as a discovery mechanism. While this access control is respected during `findMany` operations, it was not completely enforced during `update` and `delete` mutations when accepting more than one unique `where` values in filters.

This has no impact on projects using `isFilterable: false` or `defaultIsFilterable: false` for sensitive fields, or if you have otherwise omitted filtering by these fields from your GraphQL schema. (See workarounds)

# Patches This issue has been patched in `@keystone-6/core` version 6.5.0.

# Workarounds To mitigate this issue in older versions where patching is not a viable pathway.

- Set `isFilterable: false` statically for relevant fields to prevent filtering by them earlier in the access control pipeline (that is, don't use functions) - Set `{field}.graphql.omit.read: true` for relevant fields, which implicitly removes filtering by these fields your GraphQL schema - Deny `update` and `delete` operations for the relevant **lists** completely (e.g `list({ access: { operation: { update: false, delete: false } }, ... })`)