<?xml version="1.0"?> <!-- This only works on IIS 7 or later. See https://www.iis.net/configreference/system.webserver/security/requestfiltering/fileextensions --> <configuration> <system.webServer> <security> <requestFiltering> <fileExtensions allowUnlisted="false" > <clear /> <add fileExtension=".html" allowed="true"/> </fileExtensions> </requestFiltering> </security> </system.webServer> </configuration>