Open your functions.php file and paste the following function in it:
function show_file_func( $atts ) { extract( shortcode_atts( array( 'file' => '' ), $atts ) ); if ($file!='') return @file_get_contents($file); } add_shortcode( 'show_file', 'show_file_func' );
Once done, you can use the shortcode. It’s pretty simple:
[show_file file="http://www.test.com/test.html"]
Thanks to Vladimir Prelovac for the handy tip!