OpenAI Redis caching bug exposes user conversation history
Date: 2023-03
Affected: OpenAI ChatGPT — ~1.2% of Plus subscribers; conversation titles visible to other users
Attack vector: other
Category: real-world
Severity: High

A bug in OpenAI's Redis client library (redis-py) caused a race condition that allowed some ChatGPT users to see the chat history titles and first messages of other users' conversations. Additionally, payment information (name, email, address, last four digits of credit card, and card expiry date) of approximately 1.2% of ChatGPT Plus subscribers was exposed to other subscribers during a 9-hour window. OpenAI took ChatGPT offline, identified and patched the bug, and notified affected users.

Impact: PII exposure including payment details; cross-session conversation data leak; mandatory data breach disclosure; 9-hour service outage

Mitigations:
Tenant isolation testing as part of deployment validation — verify session boundaries under concurrent load
Automated cross-session data bleed detection in observability stack
Zero-trust data access model — each request must explicitly prove session ownership
Penetration testing of caching layer and session management

Architectural layers (MAESTRO):
label: Deployment & Infrastructure
notes: Redis client race condition in caching layer — infrastructure defect, not model defect
role: origin
label: Security & Compliance
notes: Data isolation between user sessions failed; detection required user reports rather than automated monitoring
role: blind-spot