404.11 from URL part !2fo%3a92c8dd8d-1ae6-40e7-9347-f2d4f728eeea

Troy Hughes 1 Reputation point

I read up on the possible causes of 404.11 and from what I can tell I'm not using any of the possible special characters that would cause a 404.11. Can someone enlighten me on why the !2fo%3a92c8dd8d-1ae6-40e7-9347-f2d4f728eeea portion of this URL is invalid?


I know that the following works.


However adding the following to that URL part seems to trigger the 404.11.


Please note I'm using the version of IIS Express that comes with Visual Studio 2019 v16.10.1

A set of technologies in the .NET Framework for building web applications and XML web services.
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  1. Sam Wu-MSFT 7,286 Reputation points Microsoft Vendor

    @Troy Hughes

    The error indicates that the Webserver is having a problem with the presented URI, double Escaped characters in the URL, which are a standard currently for URL's are blocked by the Webserver.

    To resolve this issue, the Request Filtering Module need to either disabled, or configured to allow and pass through in the URI request the double escaped characters.

    You can set the allowDoubleEscaping attribute in applicationHost.config. %windir%\System32\inetsrv\config\applicationHost.config

            <requestFiltering allowDoubleEscaping="true"/>  

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