A new API endpoint introduced in pretix 2025 that is supposed to return all check-in events of a specific event in fact returns all check-in events belonging to the respective organizer. This allows an API consumer to access information for all other events under the same organizer, even those they should not have access to.
These records contain information on the time and result of every ticket scan as well as the ID of the matched ticket. Example:
{ "id": 123, "successful": true, "error_reason": null, "error_explanation": null, "position": 321, "datetime": "2020-08-23T09:00:00+02:00", "list": 456, "created": "2020-08-23T09:00:00+02:00", "auto_checked_in": false, "gate": null, "device": 1, "device_id": 1, "type": "entry" }
An unauthorized user usually has no way to match these IDs (position) back to individual people.
Exploitability
AV:NAC:LAT:PPR:HUI:NVulnerable System
VC:LVI:NVA:NSubsequent System
SC:HSI:HSA:H5.5/CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:N/VC:L/VI:N/VA:N/SC:H/SI:H/SA:HOther