Index: wp-activate.php
===================================================================
--- wp-activate.php	(revision 43958)
+++ wp-activate.php	(working copy)
@@ -126,7 +126,7 @@
 			} else {
 				?>
 				<h2><?php _e( 'An error occurred during the activation' ); ?></h2>
-				<p><?php echo $result->get_error_message(); ?></p>
+				<p><?php echo esc_html($result->get_error_message()); ?></p>
 				<?php
 			}
 		} else {