SVG fix for WP 4.7.1+

gistfile1.txt

add_filter('wp_check_filetype_and_ext', 'ignore_upload_ext', 10, 4);
function ignore_upload_ext($checked, $file, $filename, $mimes){

    //we only need to worry if WP failed the first pass
    if(!$checked['type']){
        //rebuild the type info
        $wp_filetype = wp_check_filetype( $filename, $mimes );
        $ext = $wp_filetype['ext'];
        $type = $wp_filetype['type'];
        $proper_filename = $filename;

        //preserve failure for non-svg images
        if($type && 0 === strpos($type, 'image/') && $ext !== 'svg'){
            $ext = $type = false;
        }

        //everything else gets an OK, so e.g. we've disabled the error-prone finfo-related checks WP just went through. whether or not the upload will be allowed depends on the <code>upload_mimes</code>, etc.

        $checked = compact('ext','type','proper_filename');
    }

    return $checked;
}