Microsoft Now Blocks over 140 File Extensions
Microsoft has blocked 142 file extensions that it sees as at risk or that are typically sent as malicious attachments in emails. The move is to protect email users from what it sees as at-risk file attachments, which are typically sent with malicious scripts or executables. will prevent users from downloading email attachments with various file extensions, including ones associated with Python, PowerShell, digital certificates, Java and more. Overall, Microsoft had blocked 104 file extensions from Outlook.
Microsoft said that a lot of the newly blocked file types are rarely used, so most organizations will not be affected by the change. If you send and receiving affected attachments, they will report that they are no longer able to download them.
Microsoft will also block various extensions being used by vulnerable applications, which could be used to exploit security vulnerabilities in third-party software. According to Microsoft, they are being blocked for the benefit of organizations that might still have older versions of the application software in use.
Blocking some suspicious file extensions is common for email providers as they try to protect email users from malicious attachments. Google has a similar policy for its Gmail email service and has blocked certain types of files, including their compressed form.