Guardrails And Safety medium
Your chat UI renders model output as markdown. A red-teamer plants text in a retrieved page that makes the model emit . The user's browser fetches the image and leaks the data. Which mitigation addresses the channel itself?
- A Render images only from an allow-listed set of domains or through a proxy, and neutralize other external URLs in the output.
- B Add a system prompt rule forbidding the model from placing conversation content inside any URL it generates in a response.
- C Require HTTPS for all rendered image URLs so the data in the query string is encrypted in transit and unreadable to attackers.
- D Limit each response to one rendered image so the amount of data an attacker can exfiltrate per turn stays very small.
Answer: A. Render images only from an allow-listed set of domains or through a proxy, and neutralize other external URLs in the output.
Exfiltration rides on a **URL the client fetches automatically**, so the fix belongs in the renderer: allow-list image domains or proxy them, and neutralize other external links. The tradeoff is losing arbitrary inline images, which matters only when users need rich external content. A system prompt rule (B) is tempting but injected text can override it, and HTTPS (C) encrypts the data on its way to the attacker, who still receives it.
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