Unreported Security Loophole in ChatGPT Agent Exposes Sensitive Gmail Data for Unauthorized Access
In a significant security incident, a zero-click vulnerability was discovered in ChatGPT's Deep Research agent. The vulnerability, reported to OpenAI on June 18, 2025, was marked as resolved on September 3, 2025.
The attack originated from within OpenAI's infrastructure, making it invisible to conventional enterprise security measures. It began with an attacker sending a specially crafted email to a victim. The email contained hidden prompts that used social engineering tactics to bypass the agent's safety protocols.
Once the agent processed the malicious email, it would search the user's inbox for Personally Identifiable Information (PII). The data exfiltration occurred entirely within OpenAI's cloud environment, executed by the agent's own browsing tool. This marked a significant escalation from previous client-side attacks that relied on rendering malicious content in the user's browser.
The vulnerability's principles could be applied to any data connector integrated with the Deep Research agent. This means that any service that allows text-based content to be ingested by the agent could have served as a potential vector for this type of attack. Malicious prompts could be hidden in PDFs or Word documents in Google Drive or Dropbox, meeting invites in Outlook or Google Calendar, records in HubSpot or Notion, messages or files in Microsoft Teams, and README files in GitHub.
The tactics included asserting authority, disguising malicious URLs, mandating persistence, creating urgency, and falsely claiming security. The flaw was leveraged through a sophisticated form of indirect prompt injection.
Researchers suggest a robust mitigation strategy involves continuous monitoring of the agent's behaviour to ensure its actions align with the user's original intent. The vulnerability allowed attackers to exfiltrate sensitive data from a user's Gmail account, highlighting the importance of such measures.
OpenAI has not yet disclosed the name of the research team or individual who discovered the security vulnerability in the ChatGPT Deep Research Agent. However, they have confirmed that a fix was deployed in early August, ensuring the safety and security of their users.
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