Parse Server is an open source backend that can be deployed to any infrastructure that can run Node.js. Prior to 9.6.0-alpha.35 and 8.6.50, when a Parse.Cloud.afterLiveQueryEvent trigger is registered for a class, the LiveQuery server leaks protected fields and authData to all subscribers of that class. Fields configured as protected via Class-Level Permissions (protectedFields) are included in LiveQuery event payloads for all event types (create, update, delete, enter, leave).

Any user with sufficient CLP permissions to subscribe to the affected class can receive protected field data of other users, including sensitive personal information and OAuth tokens from third-party authentication providers. The vulnerability was caused by a reference detachment bug. When an afterEvent trigger is registered, the LiveQuery server converts the event object to a Parse.Object for the trigger, then creates a new JSON copy via toJSONwithObjects().

The sensitive data filter was applied to the Parse.Object reference, but the unfiltered JSON copy was sent to clients. The fix in versions 9.6.0-alpha.35 and 8.6.50 ensures that the JSON copy is assigned back to the response object before filtering, so the filter operates on the actual data sent to clients. As a workaround, remove all Parse.Cloud.afterLiveQueryEvent trigger registrations.

Without an afterEvent trigger, the reference detachment does not occur and protected fields are correctly filtered.