Varonis Threat Labs has disclosed CVE-2026-42824, a critical vulnerability dubbed SearchLeak that affects Microsoft 365 Copilot and allows attackers to exfiltrate data through a sophisticated three-stage attack chain exploiting LLM scope violations. The vulnerability, disclosed on June 15, 2026, represents a fundamental flaw in how AI-powered productivity tools enforce access controls over enterprise data. Organizations relying on Microsoft's Copilot for workplace assistance now face potential exposure of sensitive documents, emails, and collaboration data they assumed was properly gated by the platform's permission model.

How SearchLeak Works

The attack leverages what Varonis describes as a scope violation in how Microsoft 365 Copilot processes user queries against its knowledge base. By crafting malicious prompts across multiple interaction stages, an attacker can trick the LLM into retrieving and surfacing information that should be outside the user's normal permission boundaries. This isn't a traditional injection attackβ€”it's more insidious, exploiting the gap between what users can access through standard interfaces versus what the underlying AI model can retrieve when prompted in specific ways.

The Three-Stage Attack Chain

According to Varonis Threat Labs' analysis, the vulnerability unfolds across three distinct phases. First, the attacker establishes a foothold by extracting metadata about available documents and data structures within an organization. Second, they probe the system's boundaries using carefully constructed queries designed to map out access patterns. Finally, in the third stage, they leverage accumulated intelligence to pull sensitive data that should have been restricted based on role-based permissions.

Enterprise Implications

For enterprises, this vulnerability raises serious questions about trusting AI assistants with privileged access to corporate data stores. Microsoft 365 Copilot is marketed as a secure way to unlock insights from organizational knowledge while respecting existing permission structures. SearchLeak demonstrates that these guarantees have cracksβ€”attackers who compromise a single user account could potentially harvest far more information than that account should legitimately access.

Mitigation and Response

Security teams should audit their Microsoft 365 Copilot configurations immediately and review which users have AI assistant privileges. Organizations may need to implement additional monitoring for unusual query patterns or data exfiltration attempts through the Copilot interface. Microsoft's official guidance on CVE-2026-42824 should be followed closely as patches or configuration changes become available.

Key Takeaways

  • SearchLeak (CVE-2026-42824) exploits LLM scope violations in Microsoft 365 Copilot, not traditional injection techniques
  • The three-stage attack allows attackers to exceed their permission boundaries and access restricted corporate data
  • Organizations should audit Copilot access privileges and monitor for anomalous query patterns

The Bottom Line

This vulnerability is a wake-up call for enterprises treating AI assistants as inherently safe wrappers around sensitive data. Scope enforcement in LLMs is still maturing, and attackers are already probing these boundaries. Don't assume your Copilot implementation respects permissions it was designed to enforceβ€”assume breach mental models apply here too.