CoPhish and the Agentic Consent Problem: OAuth Phishing for the Agent-Builder Era

CoPhish, disclosed by Datadog Security Labs in October 2025, demonstrated how Microsoft Copilot Studio could be used to host OAuth consent phishing on a legitimate Microsoft domain, directing users to malicious app consent requests and silently exfiltrating resulting tokens through server-side workflow actions. The technique can affect ordinary users with permitted Microsoft Graph scopes as well as privileged administrators capable of granting broader permissions, while evading common defenses based on suspicious domains, certificates, browser traffic, and MFA. Its broader significance is that many agent builders, low-code automation tools, MCP marketplaces, and integration platforms share the same structural risk when they allow configurable login flows and automated post-consent actions under a trusted platform domain. Recommended safeguards include allowlisting redirect destinations, restricting and auditing post-authentication actions, using narrowly scoped audience-bound tokens, separating agent-building privileges from approval for sensitive scopes, and correlating agent creation with consent-grant events. Microsoft’s Entra Agent ID and WorkOS Agent Auth reflect a wider shift toward treating agents as distinct, auditable identities with short-lived and revocable permissions, though secure product design remains necessary to prevent consent traps from being created in the first place.

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