Senky

Update: no, the problem is not in the filter. The problem is in using array at all:

return array( 'file' => $new_file, 'url' => $url, 'type' => $type )
using this, script will not stop.

return $new_file
script goes fine.

I have no idea… ??

Yes, it is the same with default theme and all plugins deactivated.
I can try to install vanilla WordPress to some subdirectory, and check for the problem again, however it will not help to our problem much, as the site is already filled with the information, so that I cannot afford deleting it all.

What I inspected so far is, that problem lays in wp-admin/includes/file.php, line 345:
return apply_filters( 'wp_handle_upload', array( 'file' => $new_file, 'url' => $url, 'type' => $type ), 'upload' );
Removing apply_filters(), the script goes fine. But with it, it never stops. I tried to list all functions registered to this filter using https://stackoverflow.com/questions/5224209/wordpress-how-do-i-get-all-the-registered-functions-for-the-content-filter however no is registered.

Any ideas?

Like the longer I wait at the page where upload started, the more images are created. I assume this rely on the server resources, but it is about 15 images per second.

Disabled all plugins: did not help
Switched to Tventy Twelve: did not help
Replaced wp-admin and wp-includes with new files: did not help

I noticed, that fie uploader will upload small (0.5kb) files without problems, but it creates creates tons of images, when uploaded image is biger (20kb). There is not exception in the name of file – it is not able to properly upload file called “a.jpg”. Also there is no difference in uploading jpg or png.

I really tried everything and I have no idea how to resolve this problem. Do you have any clue? At leat to direct me to file where file uploading is handled, so that I can inspect it (I am programmer, I can debug that, but I have no idea where upload process is performed).

Also, when I attach image to new topic I want to create in forum (bbPress) (using GD bbPress Attachments – which uses native multimedia library), it creates bunch of new topics – pretty just like when I am uploading an image – the more I wait, the more topics it creates. All look identical, but each uses another file as an attachment.

No JS errors.

As I told already, this problem appears also using browser uploader, which uses, I believe, no JS at all.