[BitBucket user: Sébastien Jodogne]
[BitBucket date: 2018-12-21.08:43:43]

This issue normally only arises only on Firefox, but this assumption has not been thoroughly tested, so the popup warning is displayed on any browser (including Chrome/Chromium even if it should not be affected).

Solving this issue would require a refactoring of Orthanc Explorer (update of the "jquery-file-upload" library, that would in turn need an update of jQuery Mobile, which would eventually lead to very deep modifications because backward compatibility is not ensured in the framework). As an alternative solution, we could separate the upload page from the main jQuery Mobile application, enabling us to use a different framework.

Check also the remarks about "Orthanc Explorer 2": http://book.orthanc-server.com/faq/improving-interface.html