2.2.26 [W3C-HTML52] Section 4.10.21.7. Multipart form data

C0044: Form fields, including filename fields, are encoded in UTF-8 and are not approximated

The specification states:

 ... Multipart form data
     ...
     The multipart/form-data encoding algorithm is as follows:
         ...
         5.  ...
             File names included in the generated multipart/form-data resource (as part of 
             file fields) must use the character encoding selected above, though the 
             precise name may be approximated if necessary (e.g. newlines could be removed 
             from file names, quotes could be changed to "%22", and characters not 
             expressible in the selected character encoding could be replaced by other 
             characters). ...

EdgeHTML Mode

Form fields, including filename fields, are encoded in UTF-8 and are not approximated.