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.

https://office365itpros.com/2023/06/26/teams-external-access-exploit/