TLDR: MS Teams' guest access may compromise security, allowing users to bypass Microsoft Defender protections when joining external tenants. This vulnerability could let attackers create “protection-free zones,” using low-cost licenses to exploit unprotected environments, leading to phishing attacks. Organizations should restrict guest invites to trusted domains and enhance security measures.
https://thehackernews.com/2025/11/ms-teams-guest-access-can-remove.html