Extra GET request when using SWFUpload

I've been using SWFUpload for quite a long time now. Put simply, it's a Flash/Javascript plugin allowing a file upload to be done without having to submit the page.

Basically it uses the streaming upload capacity of flash to fire javascript events to tell the developer the upload percentage, do some filesize and filetype checks, etc.

If you've ever seen an upload progress bar on any website, it most surely was done using SWFUpload.

Anyway, today I spotted a strange behavior in one of my pages, heavily using SWFUpload (more or less 20 upload fields). Using the Net panel of Firebug, I saw some strange GET requests being made to my website.

After digging into my code, I could isolate the problem. I was coming from SWFUpload itself. I even found record of a bug report mentionning it.

In a nutshell, SWFUpload always make a request to the url specified in the button_image_url parameter, even if you haven't specified one (in this case it made a request to your webroot).

I'm not using any image for my button, or should I say, I take care of that in CSS already, my SWFUpload button is just an invisible Flash element, positionned on top of my existing button.

I tried setting the value to null, false or an empty string, but it would continue to do the request.

Anyway, I upgraded to the latest version (2.5.0 Beta 3), and it solves my problem. Now I'm just hoping that all the retro-compatibility will be kept.