This article was created in response to a support issue logged with K2. The content may include typographical errors and may be revised at any time without notice This article is not considered official documentation for K2 software and is provided "as is" with no warranties.


An error appears when trying to upload a file using the file attachment control.

"The file could not be uploaded. Unforeseen error occurred on the file upload, contact your administrator".



  • The issue occurs across all browsers and for any file size and type. 

  • You are able to consistently get the error when uploading a file. 

Troubleshooting Steps

Please check if ASP.NET Impersonation authentication is enabled on the K2 Designer and Runtime application on IIS. If so, perform the following steps to resolve this:

1. On IIS, navigate to the K2 Designer and Runtime app > Authentication

2. Disable ASP.NET Impersonation authentication


3. Perform an IISRESET

4. Access your Smartforms and test the upload