What leaks: User data, PII, training data, proprietary algorithms, business data.
Source: Data the model was trained on, or data in its context window from other users or sources.
Example: ChatGPT repeats another user’s chat history due to a Redis bug (March 2023).
Defense: Sanitize training data, enforce access controls, output filtering.
What leaks: The developer’s own instructions — the prompt itself.
Source: Content the developer intentionally put in the system prompt.
Example: Bing Chat reveals its “Sydney” prompt when asked to ignore prior instructions (Feb 2023).
Defense: Don’t put secrets there. Don’t rely on secrecy.