Recent cybersecurity research has uncovered a new proof-of-concept technique called the Teams Cookie BOF, a specialized Beacon Object File (BOF) that demonstrates how authentication cookies in Microsoft Teams could be extracted under certain conditions. While the research is not malicious in intent, it highlights potential weaknesses in how collaboration tools handle sensitive data — and why defenders must understand token security more deeply.
Understanding the Background
The tool, released by Tier Zero Security, builds on prior findings from RandoriSec, which analyzed how Microsoft Teams manages user authentication. Teams uses the msedgewebview2.exe process — a Chromium-based webview — to log users into Microsoft 365 services.
During this login process, authentication cookies are stored locally in a SQLite database, similar to how web browsers store session data. These cookies contain tokens that grant access to Teams chats, files, and other Microsoft 365 resources.
The purpose of the research was not exploitation, but to demonstrate a security gap: these tokens, if improperly protected, could be misused to impersonate users or access enterprise information.
How the Research Developed
Modern browsers have strengthened their defenses using a component called the IElevator service, which secures cookie decryption under SYSTEM privileges. This service checks whether a process trying to access cookies is a legitimate browser component.
However, Microsoft Teams uses a simpler Data Protection API (DPAPI) model tied to the current user account. This difference means Teams’ cookie data, while encrypted, may be more accessible once an attacker gains access to a user’s environment.
The Teams Cookie BOF research explored how to read cookie data without terminating the Teams process, which would alert users or trigger security events. Instead, it adapts a method originally developed for browser research (known as Cookie-Monster-BOF) to analyze Teams’ live data in a controlled, academic setting.
What the Researchers Found
The proof of concept demonstrates that Teams cookies are accessible via legitimate Windows processes when using the same user context. Because Teams locks its database file during use, the BOF bypasses these locks conceptually through handle duplication and memory access — all within the confines of the active Teams process.
The idea is to show that process-in-memory protection can be a potential blind spot if applications rely solely on DPAPI for token storage.
The findings do not exploit users, crash Teams, or bypass authentication. Instead, they raise awareness of endpoint data exposure risks that security teams should consider when evaluating application architecture.
Why This Matters for Enterprises
- Identity exposure: Authentication cookies function as access tokens — if stolen or copied, they could grant temporary access to corporate resources.
- Endpoint security gaps: Collaboration tools run continuously on most workstations, making their runtime environment a target for credential misuse.
- Threat detection challenges: Modern endpoint protection tools may not easily distinguish between normal and abnormal process handle operations.
- Growing attack surface: With more enterprise tools embedding webview components, cookie and token protection must evolve beyond standard encryption.
Defensive Takeaways
While this research is academic, it underlines essential security lessons for enterprises:
- Review authentication token storage — Ensure that sensitive cookies or tokens are stored securely using system-level protection mechanisms.
- Implement strong access controls — Restrict who can access or manipulate application data files at runtime.
- Enhance monitoring — Watch for unusual process activity involving Teams, browsers, or webview components.
- Educate users — Encourage awareness about session persistence, token reuse, and logging out of shared devices.
- Engage vendors — Work with software providers to adopt stronger cryptographic protections and telemetry around authentication artifacts.
These steps form part of a healthy defense-in-depth approach to identity and session security.
The Bigger Picture
The Teams Cookie BOF isn’t an attack kit — it’s a research framework that highlights how authentication handling in modern desktop applications can create potential risks if not carefully designed. Microsoft and other vendors regularly improve these mechanisms, but enterprise defenders should remain vigilant.
This discovery aligns with a broader industry trend: endpoint identity protection is now just as important as network and perimeter defenses. As cloud tools and embedded browsers become ubiquitous, ensuring that authentication tokens remain secure in memory and at rest is a top priority.
Conclusion
The Teams Cookie BOF research emphasizes an important cybersecurity truth: security isn’t only about encrypting data — it’s about controlling where, how, and by whom it can be accessed.
Organizations that proactively review token management, strengthen telemetry, and apply least-privilege principles will be far better positioned to mitigate risks arising from token-based authentication.
In short, this research is a reminder that user trust and authentication data deserve the same level of protection as passwords.
