Wordpress: An error occurred in the upload

Question

After updating to WordPress 3.5, I started getting the following error when uploading files using the Add Media button as a non-admin user:

Error: An error occurred in the upload. Please try again later.

The image seems to finish uploading, but right at the end this error message appears.

This doesn't happen for the administrator, only the other roles. I've even tried giving the other role full admin capabilities, but the error still appears.

Is this a bug? Or am I missing something?

Answer 1

After much trial and error, I finally found a solution that worked for me.

First, I found the following role capabilities to be required to upload files for custom user roles:

$capabilites = array(

    'read'                  => true,
    'upload_files'          => true,
    'edit_published_pages'  => true,
    'edit_others_pages'     => true

);

I'm not sure why these are specifically required, but the error kept occurring without them.

Second, I had to update a function I was using to prevent non-admin users from accessing the Dashboard:

function redirect_nonadmin_fromdash(){

    if($_SERVER['PHP_SELF'] == '/wp-admin/async-upload.php'){

        /* allow users to upload files */

        return true;

    } else if(get_user_role() != 'administrator'){

        /* custom function get_user_role() checks user role, 
        requires administrator, else redirects */

        wp_safe_redirect(home_url());
        exit;

    }

}

add_action( 'login_form_login', 'redirect_nonadmin_fromdash' );
add_action( 'admin_init', 'redirect_nonadmin_fromdash', 1 );

Previously, I was checking for the media-upload.php, but the new media uploader uses async-upload.php.

So, essentially, this allows non-admin users to use the new media uploader from the front-end without allowing them access to the Dashboard.

It also restricts their access to the Media Library, which was also important to me.