Thanks for the extra information. When using Safari for Windows (instead of the Mac version) I can also reproduce this issue with Community 6.012. It appears to be related to a third party upload component which also has an incompatibility with Safari/Windows.
The issue is corrected in the most-recent hotfix version of 6.0 when using Safari for Windows.
I also have not been able to reproduce the issue yet with with Safari for Mac, even with 6.012.
I recommend requesting a 6.0 hotfix update from support.