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https://msrc.microsoft.com/update-guide/vulnerability/CVE-2021-1730
Change Image Download URL
Basically, you need to change both the external & internal download hostname to a different domain name.
Launch the Exchange Management Shell, and execute the following commands
Set-OwaVirtualDirectory -Identity "owa (default Web site)" -ExternalDownloadHostName “Images.DeepnetID.com"
Set-OwaVirtualDirectory -Identity "owa (default Web site)" -InternalDownloadHostName "Images.DeepnetID.com"
Set-OrganizationConfig -EnableDownloadDomains $true
Add URL Binding
On the Exchange server, launch the IIS Management
Select the OWA node, and launch the DualShield IIS Agent console
Click "URL Bindings"
Add the image download URL in to the URL Bindings
Apply the change
Add HTTP Filter
We also need to add a HTTP Filter.
Click "HTTP Filter"
Add the following HTTP filter
- Header: sec-fetch-dest
- Value: image
Apply the change.