According to this bug (https://connect.microsoft.com/IE/Feedback/Details/868498), multipart form data is malformed if there are fields without names. This bug has been solved within Edge browser, however no solution is expected for IE10/IE11
Related issues
Bug #17808: Editing provisioning templates on Internet Explorer fails with Internal Server Error
Added by Amir Fefer over 7 years ago
Fixes #17808 - fix 'multipart form data' IE bug
According to this bug
(https://connect.microsoft.com/IE/Feedback/Details/868498),
multipart form data is malformed if there are fields without names.
This bug has been solved within Edge browser,
however no solution is expected for IE10/IE11