Error with the Flash Uploader in Firefox


Active member
The flash uploader for files is broken with Firefox 38.0.5. When trying to upload an image on my XenForo this error appears:

If I disable the option "Use Flash Uploader" the normal upload works. With Chrome or Opera the flash uploader is working.

I hope there is a solution for this bug. I would like to use the flash uploader, but so this is not possible.


Active member
It seems here it's working:
Tardis in Morrowind.jpg

But I've tested the flash uploader with a XenForo on two different virtual servers (Ubuntu 12.04 and 14.04), on both the error appears, even directly after the installation of the XenForo without addons.

For other users, this error also appears.
Last edited:


XenForo developer
Staff member
Is the site you're testing on behind password protection (such as via .htaccess)?

If it works here, it would imply there's something distinct with your setup. This could be what I suggested above, or it could be a server configuration outside of XenForo.


Active member
Oh, such an easy solution... The XenForo is password protected via .htaccess. After removing it, the flash uploader is working on Firefox. Strange thing.

Then it's not that important, only our test site will be password protected later.