HTTP Error 404.11 - Not Found
The request filtering module is configured to deny a request that contains a double escape sequence.
The request contained a double escape sequence and request filtering is configured on the Web server to deny double escape sequences.
This is a security feature. Do not change this feature unless the scope of the change is fully understood. You should take a network trace before changing this value to confirm that the request is not malicious. If double escape sequences are allowed by the server, modify the configuration/system.webServer/security/requestFiltering@allowDoubleEscaping setting. This could be caused by a malformed URL sent to the server by a malicious user.

Upload Image

   1. Log in as admin plain admin
   2. Click "Media library" in top menu
   3. Click "Files" link
   4. Select "file" in drop down and click "Create here" button next to it
   5. Enter formdata:
      Name : testfile
      Description : Our file description
      New file for upload : [select a .txt file from your harddrive]
   6. Click "Send for publishing button

View the file object and download the file

   1. Click "Preview" tab
   2. Click "test file" link
   3. Verify that you see the name and description:
      test file
      Our file description
   4. Verify that you have a link named with the same name as the file you uploaded
   5. Click on that link (ref #4) and download the file
   6. Verify that the content of the downloaded file is the same as in the file you previously uploaded