media_sideload_image() doesn't handle dynamic image url's well

[dd32]

Example URL: ​http://www.tumblr.com/photo/1280/10464566223/1/tumblr_lrum2xzkpC1r3z8e3

As a result, the preg_match() for the file extension fails and issues a notice (no file extension in that url, although the redirection location does have).

The handling of a download failure also seems hairy, upon failure, it still attempts further importing before loading - I haven't looked into that too far.

Probably not relevant for your use case, and I'm sure you're very well aware of the filter, but I was able to get around a similar bug by modifying the wp_check_filetype_and_ext filter as such -

add_filter( 'wp_check_filetype_and_ext', 'gd_pdf_bypass' );

function gd_pdf_bypass( $filearray ) {
    $filearray['type'] = 'image/jpeg';
    $filearray['ext'] = 1;
    return $filearray;
}

Granted, still doesn't attach properly (not necessary in my use case), but I'm able to get it to return the proper <img> tag and upload to the server with the override.

Determine file extension based on content type header

I'm having this issue with some of my users in my media-tools plugin which imports and attaches external images. I'm going to work on refreshing the patch for 3.5.