Security Researchers Demonstrate Exploit Against Teams External Access

Security Researchers JumpSec demonstrated a weakness in Teams External Access by showing how to send malware to users via a federated chat. The exploit depends on another weakness in that attackers can interfere with the set of policy controls transmitted by the Teams server to clients. It’s yet another reason why Microsoft 365 tenants should restrict external access to the set of domains they really want to chat with.

Why Teams Sometimes Won’t Allow External Users In

Teams supports external access through guest account membership in teams and external sharing of shared channels. Sometimes, things go wrong and sharing can’t happen. In this article, we explore some common reasons and explain the solutions. And the need for patience!