Exchange Online-Updates to the file type list in the common attachment filter
In anti-malware policies, you can select specific file types to identify as malware using the common attachment filter. Any email message with attachments of these specific file types will be handled per the policy settings. You can configure this specific list of file types by selecting them from the pre-defined list in the policy properties in the Microsoft 365 Defender portal or by manually adding your own (custom) file types using the power shell Set-MalwareFilterPolicy cmdlet in Exchange Online PowerShell.