This attack achieved a high success rate against state-of-the-art models, including Claude Opus 4.7.OverviewCopilot Cowork is a Frontier feature available now in Microsoft 365. It operates with the users’ Microsoft permissions and can use Microsoft Graph to read and operate on data in one’s Microsoft tenant.In this article, we demonstrate that through an indirect prompt injection in a poisoned skill, attackers can exfiltrate files from M365. This is done by exploiting the fact that, unlike other...