Index: wp-content/themes/twentythirteen/style.css
===================================================================
--- wp-content/themes/twentythirteen/style.css	(revision 25689)
+++ wp-content/themes/twentythirteen/style.css	(working copy)
@@ -1738,8 +1738,7 @@
 	max-width: 104px;
 }
 
-.attachment footer.entry-meta,
-.single-attachment .site-main .sidebar-container {
+.attachment footer.entry-meta {
 	display: none;
 }
 
Index: wp-content/themes/twentytwelve/css/ie.css
===================================================================
--- wp-content/themes/twentytwelve/css/ie.css	(revision 25689)
+++ wp-content/themes/twentytwelve/css/ie.css	(working copy)
@@ -53,7 +53,7 @@
 	width: 65.104166667%;
 }
 body.template-front-page .site-content,
-body.single-attachment .site-content,
+body.attachment .site-content,
 body.full-width .site-content {
 	width: 100%;
 }