When you click on the icon to Export the mod to a ZIP or JAR file and select the same file name on a drive you want to write to (basically overwrite existing), the file is not overwritten and there is a new file created with the name chosen with a second .jar in the name. (abcdeFGH.jar.jar) If a user wants to overwrite an existing file, they should be able to by being prompted with a dialog to confirm.
Issue comments
Thanks - I've tried both typing in the name and selecting the file from my folder and both there are no warnings like you say, but it also doesn't overwrite them. I get files with double .jar on them. If I repeat this process,it will again add another .jar to the file. Weird behavior, but that's what I see.
If you only enter the name without the extension, it will overwrite the file, I have tested this right now. But it does not warn you about the overwriting, so I will keep this issue open until we implement the overwrite warning dialog. Thank you for reporting this bug.