Flash Uploader Issue


Well-known member

We have just upgraded to PHP 5.4.15 and it seems that the only thing to have stopped working is the Flash file uploader. Whenever we try and upload in FF, we are met with this error:


No error is logged for this, in the ACP.


XenForo developer
Staff member
Just to confirm, it doesn't happen in FF with the Flash uploader disabled?

Can you check your web server error log? There might be more information there.

What version of PHP were you running before?


Well-known member
Hi Mike,

I can confirm, the non-flash uploader works fine in FF.
We were running 5.2.9 previously.

I will speak to my server guy about getting log information...


Well-known member
This has to do with the mod_security settings.

Here is the ticket I have had to send it to get it corrected:

If you believe the security rule is affecting the normal operation of your website,
you can disable it by adding the following lines to your .htaccess file:

<IfModule mod_security.c>
# Turn the filtering engine On or Off
SecFilterEngine Off

Could you disable that please?

Floyd R Turbo

Well-known member
I am getting this issue as well, after searching through this site on attachment uploading issues I've pinned down the problem to the Flash Uploader. If I disable it, I can use the "Upload a File" button. If it is enabled, I cannot use the button, but I can drag & drop the file into the editor window and that works.

So in reference to this statement:

Rather than turning mod_security off entirely for the site, you should find the actual rule that's kicking in and fix that instead.
What rule do I need to look for here?

I know nothing about mod security, does it open up the potential for harm to disable it completely in .htaccess by removing the # from the lines as described in the file?

Is there a better way, like this? https://xenforo.com/community/threads/disabling-mod_security-on-xenforo.41744/#post-449761

Floyd R Turbo

Well-known member
No, I saw that one but I have dual monitors and the pop up goes into the other monitor.

My issue is identical to the OP, the photo loads up (the progress bar gets to 100%) and then I get the "problem uploading your file" pop up.


XenForo developer
Staff member
Just to note that mod_security can't always be adjusted from .htaccess (probably true more often than not). Your host should be able identify the rule that is being hit and whitelist it for your account.

Floyd R Turbo

Well-known member
I figured this one out. The issue was not related to mod security at all. The issue was occurring on an installation that is currently password protected as it is a dry-run conversion that is under construction. It turns out that password protecting the XF installation directory will interfere with the flash uploader.

I figured this out because another XF license I'm running with the same host did not exhibit the issue. I removed the PW protection and the flash uploader worked, then put the protection back on without refreshing the page and the flash uploader failed.

So just FYI for anyone seeing the same issue on a test installation, that's the reason. Disable the uploader in ACP and then enable it when you go live, problem solved.