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MEDIUMAI/LLMexploited in the wild

AI-GEMINI-WORKSPACE-2025

Google Gemini · Gemini for Workspace email summarization

Summary

Marco Figueroa of Mozilla's 0DIN program documented a Gemini for Workspace flaw where an attacker hides instructions inside an email using tags styled with font-size zero or white-on-white text, invisible to the recipient. When the user clicks Summarize this email, Gemini processes the raw HTML and treats the hidden directive as a high-priority instruction, appending an attacker-crafted fake security warning, such as a fake support phone number, that appears to come from Google. No links or attachments are required, enabling credential harvesting and vishing at scale through indirect prompt injection.

How to avoid it in your code

  • Strip hidden HTML (font-size zero, white-on-white) before the model summarizes email.
  • Treat email content as untrusted data, not high-priority instructions.
  • Sanitize/encode model output so injected fake warnings and phone numbers are not surfaced as trusted.
  • Flag AI summaries as untrusted and warn users not to act on embedded contact details.
  • Apply input guardrails to detect injected directives in retrieved content.

References

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