[Mediawiki-l] Correct way to modify specialupload.php?

[Tech Geek]

I want to comment out couple of lines of code in the file
/var/lib/mediawiki/includes/specialupload.php file. Here are the lines:
  //if( $this->detectScript ( $tmpfile, $mime, $extension ) ) {
  // return new WikiErrorMsg( 'uploadscripted' );
  //}
Now I know that it is not a good idea to modify the core mediawiki files.

What is the correct way to do this then?