What happened
A newly disclosed Microsoft Copilot vulnerability shows how an AI assistant can be talked into exposing its own security secrets. Researchers at security firm Varonis wanted to find out whether Microsoft 365 Copilot for enterprise could be tricked into leaking sensitive data without any real user consent. Instead of reverse-engineering the software, they simply asked Copilot detailed questions about its own safety mechanisms — and it answered.
Copilot initially refused to auto-execute commands, correctly explaining that sensitive actions require a manual gesture, like pressing Enter. But each refusal came with an explanation, and each explanation contained a clue. Over a series of questions about URL structures, deep links, and how the input field behaves when preloaded with text, Copilot gradually revealed an undocumented parameter: ?autorun=1. Combined with the known ?q= parameter, this string let a prompt fire automatically the instant someone clicked a link — no confirmation needed.
Varonis Senior Researcher Lior Adar told Ars Technica that "every refusal revealed technical details about its internal architecture," and that the team eventually used those leaked parameters to build working exploit links. One proof-of-concept prompt instructed Copilot to search a victim's inbox, extract the latest sender's email address, and quietly send it to an attacker-controlled webhook — all triggered by a single click.
Microsoft first patched the issue in February, about three months after Varonis reported it, by blocking ?q= from injecting text directly into the chat input. A more complete fix followed later, closing the loophole that let third-party links auto-populate and auto-run commands inside Copilot.
Why it matters
This case matters because it exposes a new category of risk: AI assistants can be socially engineered the same way people are. The researchers didn't write exploit code first — they had a conversation. Copilot's own explanations of its guardrails became the blueprint for defeating them.
That's a meaningful shift for anyone building or relying on AI tools that touch email, files, or credentials. A chatbot that can open Gmail, summarize an inbox, or draft messages from a URL parameter is, by design, wired into sensitive systems. If the confirmation step protecting that access can be silently bypassed, a single malicious link becomes enough to exfiltrate data — no malware, no phishing page, no password entry required from the victim.
It also matters because the exploit reportedly wasn't limited to email addresses. A separate version of the prompt directed Copilot to search a mailbox for passwords or other credentials that had been shared in messages, then forward them to the attacker. For any organization running Copilot across a workforce, that turns an AI productivity tool into a potential single point of failure for account security.
How to use it today
For most users, the direct fix is already live — Microsoft has closed both the ?q= injection path and the ?autorun=1 bypass, so the specific exploit described by Varonis no longer works. Still, there are practical steps worth taking today:
- Avoid clicking Copilot or AI-assistant links from unknown senders, even if they look like internal tools.
- Ask your IT or security team whether Microsoft 365 Copilot logging and URL-based prompt injection protections are enabled for your tenant.
- Treat any AI assistant that can read your inbox as having the same blast radius as your email account itself, and apply the same caution to links sent to it.
- Review what third-party browser extensions or integrations are allowed to pass parameters into Copilot, since the original ?q= behavior existed to support legitimate tool integrations.
If you're experimenting with your own AI-powered workflows — for drafting content, summarizing documents, or automating small marketing tasks — it's worth using tools built with narrower, more transparent permissions rather than assistants wired deep into your email and files. Free platforms like mykreatool.com let creators and marketers run AI tasks such as writing, image generation, or content ideation without connecting an assistant directly to sensitive inboxes, which limits this kind of exposure by design.
Who benefits
The immediate winners here are Microsoft 365 Copilot users, whose accounts are now protected against this specific auto-run exploit following the February and follow-up patches. Enterprise security teams also benefit from having a documented case study: it's a concrete example to bring into AI-vendor risk assessments and staff training on prompt-injection attacks.
Security researchers and red teams benefit too. The Varonis findings demonstrate a repeatable technique — probing an LLM's own refusals for technical detail — that can be applied to test other AI assistants with similar URL-based prompt or auto-execution features, from customer-support bots to browser copilots.
Marketers and entrepreneurs who rely on AI assistants for daily workflows benefit indirectly: the disclosure pushes vendors toward tighter default security, meaning the tools available six months from now should require less manual vetting.
Risks
The core risk is that this was not a one-off bug but a demonstration of a technique. Any AI assistant that accepts prompts through URL parameters, deep links, or preloaded chat fields could theoretically be probed the same way — by asking it, politely and persistently, to explain its own limits. Twenty questions was enough to extract a Microsoft trade secret; other vendors may have similarly under-documented parameters.
There's also a lag risk: Varonis reported the flaw in November, but the first fix didn't land until February — roughly three months during which the ?autorun=1 bypass was reportedly still usable by anyone who discovered it independently. Undocumented parameters that exist for legitimate integration purposes, like ?q=, can double as attack surface if they're not scoped carefully.
Finally, credential exposure is the sharpest edge of this story. An assistant with inbox access that can be triggered to search for and forward passwords turns a single clicked link into a full account-takeover pathway, without the phishing page, fake login screen, or malware that traditional attacks usually require.
Conclusion
The Microsoft Copilot vulnerability uncovered by Varonis is a reminder that AI assistants can be interrogated into revealing their own weaknesses, and that undocumented parameters are a real attack surface. Microsoft has patched the specific exploit, but the underlying lesson — treat AI assistants with inbox or file access as high-value targets — applies well beyond this one product.
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