We cannot add several file types to a SharePoint Site with SharePoint Designer or through a WSP solution. Examples are: ashx, dll, exe, msi.
Error: "Server error: The following file(s) have been blocked by the administrator: /Style Library/Empower/images/Imfuscator.dll"
- From Microsoft: place your files in a zip and upload them packaged
- Configuring Central Admin:
Security, Define blocked file types (/_admin/BlockedFileType.aspx)
- For SharePoint Online / Office 365: Issue a "Service Request" (https://portal.microsoftonline.com/Support/ServiceRequests.aspx)