Currently, there is no direct means of controlling what type of file can be uploaded as a feature service attachment. This is very inconvenient for feature services editing. The workaround is found in editing the service properties of the REST Admin API.
The "allowedUploadFileTypes" attribute allows one to specify a list of allowed file extensions to limit which types of attachment can be uploaded to a service. There is no easy way to modify this property in ArcGIS Server Manager in the current release.
The "allowedUploadFileTypes" attribute is stored in the map service's JSON description file in the config store. It can be edited by logging in to the REST Admin page.
- Open a web browser and navigate to http://<server name>:6080/arcgis/admin/login.
and log in to the ArcGIS Server Administrator Directory with an administrators account.
- Click Services. Click the name of the service that has feature access enabled.
Go to the edit link at the bottom of the page under Supported Operations.
- In the text box for the service (in JSON format):*, find the allowedUploadFileTypes tag and add the file extensions you want to allow inside the quotations after the colon (:). A completed entry would look similar to "allowedUploadFileTypes": ".png,.gpx".
- Click the Save Edits button. Only the file types that are specified in the REST Admin can be uploaded when editing the feature service.