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Microsoft Teams will let admins block custom file extensions
September 18, 2026 · BleepingComputer · Severity: MEDIUM
Microsoft Teams will soon let administrators tweak the list of file extensions commonly associated with security threats to meet their company's security requirements.
Key Takeaways
- Microsoft Teams will now allow administrators to block custom file extensions from being uploaded or shared within the platform, giving organizations granular control over which file types can be exchanged by users.
- This feature addresses security concerns where threat actors use uncommon file extensions to bypass traditional attachment filters and deliver malware through Teams chat channels.