Keystone is a content management system for Node.js. Prior to version 6.5.0, `{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. This affects any project relying on the default or dynamic `isFilterable` behavior (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 e

Keystone has an unintended `isFilterable` bypass that can be used as an oracle to match hidden fields