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CVE-2026-26133 is an AI command injection and cross-prompt injection vulnerability in Microsoft 365 Copilot’s email summarization surfaces, including Outlook and Teams-integrated Copilot experiences. The flaw arises when Copilot processes untrusted email content and fails to reliably neutralize instruction-like text or maintain a strict boundary between attacker-controlled message content and the model’s operational instructions. As a result, text embedded in an otherwise ordinary email can be interpreted by the model as commands, allowing an attacker to influence the generated summary. Reported behavior included attacker-shaped phishing content appearing inside Copilot’s trusted summary interface and, in some scenarios, model-mediated retrieval of internal Microsoft 365 context such as collaboration data accessible through the user’s Copilot permissions. The issue is fundamentally a prompt-boundary and special-element neutralization failure in an LLM-assisted enterprise workflow.
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A previously disclosed Microsoft 365 Copilot AI command injection / information disclosure vulnerability, mentioned as part of the vendor's 2026 security history.
A cross-prompt injection issue in Microsoft 365 Copilot email summarization where attacker-controlled text embedded in an email can steer Copilot’s summary output to include convincing attacker-authored phishing content and potentially incorporate retrieved internal context into attacker-supplied links.
A Microsoft 365 Copilot email summarization cross-prompt-injection vulnerability where attacker-supplied instructions embedded in email content can steer Copilot’s generated summary (including authoritative ‘security alert’ content and links), enabling high-trust phishing and potentially chaining into cross-app retrieval (Teams/OneDrive/SharePoint) for user-assisted data exfiltration.
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Every observed campaign linking this CVE to a named adversary.
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Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.