(function () {

    // register plugin
    CKEDITOR.plugins.add('blockimagepaste', {
       
        init: function (editor) {
            
            editor.on( 'paste', function(e) {

                var html = e.data.dataValue;
                if (!html) return;
                
                // Replace data: images in Firefox and upload them
                e.data.dataValue = html.replace( /<img( [^>]*)?>/gi, function( img ) {
                    alert('Pasting images directly into the editor is not allowed. ');
                    return '';
                });
            });
    
        }
    });

})();