diff --git a/wp-admin/includes/ajax-actions.php b/wp-admin/includes/ajax-actions.php
index d8b74561bb..a6334cb69f 100644
--- a/wp-admin/includes/ajax-actions.php
+++ b/wp-admin/includes/ajax-actions.php
@@ -197,8 +197,10 @@ function wp_ajax_wp_compression_test() {
 			echo $out;
 			wp_die();
 		} elseif ( 'no' == $_GET['test'] ) {
+			check_ajax_referer( 'update_can_compress_scripts' );
 			update_site_option('can_compress_scripts', 0);
 		} elseif ( 'yes' == $_GET['test'] ) {
+			check_ajax_referer( 'update_can_compress_scripts' );
 			update_site_option('can_compress_scripts', 1);
 		}
 	}
diff --git a/wp-admin/includes/template.php b/wp-admin/includes/template.php
index bc103faa71..5138fd204c 100644
--- a/wp-admin/includes/template.php
+++ b/wp-admin/includes/template.php
@@ -1789,6 +1789,7 @@ function _media_states( $post ) {
 function compression_test() {
 ?>
 	<script type="text/javascript">
+	var compressionNonce = <?php echo wp_json_encode( wp_create_nonce( 'update_can_compress_scripts' ) ); ?>;
 	var testCompression = {
 		get : function(test) {
 			var x;
@@ -1808,7 +1809,7 @@ function compression_test() {
 					}
 				};
 
-				x.open('GET', ajaxurl + '?action=wp-compression-test&test='+test+'&'+(new Date()).getTime(), true);
+				x.open('GET', ajaxurl + '?action=wp-compression-test&test='+test+'&_ajax_nonce='+compressionNonce+'&'+(new Date()).getTime(), true);
 				x.send('');
 			}
 		},
diff --git a/wp-includes/version.php b/wp-includes/version.php
index b31925b86b..639a21c85d 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -4,7 +4,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '4.5-RC1-37135';
+$wp_version = '4.5-RC1-37143';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.