Critical Microsoft Teams Flaw Lets Hackers Manipulate Messages and Notifications

Check Point Research discovered four critical security vulnerabilities in Microsoft Teams that threaten trust in this widely used communication platform. These flaws allow both external attackers and malicious insiders to impersonate executives, alter messages without detection, spoof notifications, and forge caller identities during audio and video calls.

With 320 million monthly users depending on Teams for business communication, these security gaps present a serious risk to organizations worldwide. Attackers can exploit core messaging and calling features through several attack vectors by manipulating specific platform parameters.

Attack Methods and Impact

Impersonation of trusted colleagues and senior leadership to exploit psychological urgency.
Editing messages without leaving any audit trail by tampering with the clientmessageid parameter.
Spoofing notifications and forging caller identities during calls.

These vulnerabilities reveal sophisticated exploitation methods that could devastate organizational security.

The research highlights how attackers can craft convincing messages and calls that appear legitimate, increasing the risk of phishing, misinformation, and malicious actions within organizations.

Summary

Check Point Research’s findings expose critical flaws in Microsoft Teams that enable undetectable message tampering and impersonation, posing a significant threat to enterprise security.

Cyber Press — 2025-11-06