Google Gemini tricked into leaking private meeting data via poisoned calendar invites

What happened

Miggo Security disclosed an indirect prompt-injection flaw in Google Gemini in which hidden instructions placed in a calendar event description could override Google Calendar's privacy controls. The payload lay dormant until the victim asked Gemini a routine question about their schedule, at which point the assistant could be steered into summarising private meetings into a new calendar entry the attacker could read. The victim never had to open, accept or click anything from the attacker; an invite landing on the calendar was enough. Google addressed the issue after responsible disclosure.