diff --git a/wp-admin/includes/meta-boxes.php b/wp-admin/includes/meta-boxes.php
index 902bf95876..ef0734e329 100644
--- a/wp-admin/includes/meta-boxes.php
+++ b/wp-admin/includes/meta-boxes.php
@@ -404,9 +404,8 @@ function post_tags_meta_box( $post, $box ) {
 		$args = $box['args'];
 	}
 	$r = wp_parse_args( $args, $defaults );
-	$tax = $r['taxonomy'];
-	$tax_name = esc_attr( $tax );
-	$taxonomy = get_taxonomy( $tax );
+	$tax_name = esc_attr( $r['taxonomy'] );
+	$taxonomy = get_taxonomy( $r['taxonomy'] );
 	$user_can_assign_terms = current_user_can( $taxonomy->cap->assign_terms );
 	$comma = _x( ',', 'tag delimiter' );
 ?>
@@ -462,50 +461,50 @@ function post_categories_meta_box( $post, $box ) {
 		$args = $box['args'];
 	}
 	$r = wp_parse_args( $args, $defaults );
-	$taxonomy = $r['taxonomy'];
-	$tax = get_taxonomy( $taxonomy );
+	$tax_name = esc_attr( $r['taxonomy'] );
+	$taxonomy = get_taxonomy( $r['taxonomy'] );
 	?>
-	<div id="taxonomy-<?php echo $taxonomy; ?>" class="categorydiv">
-		<ul id="<?php echo $taxonomy; ?>-tabs" class="category-tabs">
-			<li class="tabs"><a href="#<?php echo $taxonomy; ?>-all"><?php echo $tax->labels->all_items; ?></a></li>
-			<li class="hide-if-no-js"><a href="#<?php echo $taxonomy; ?>-pop"><?php _e( 'Most Used' ); ?></a></li>
+	<div id="taxonomy-<?php echo $tax_name; ?>" class="categorydiv">
+		<ul id="<?php echo $tax_name; ?>-tabs" class="category-tabs">
+			<li class="tabs"><a href="#<?php echo $tax_name; ?>-all"><?php echo $taxonomy->labels->all_items; ?></a></li>
+			<li class="hide-if-no-js"><a href="#<?php echo $tax_name; ?>-pop"><?php _e( 'Most Used' ); ?></a></li>
 		</ul>
 
-		<div id="<?php echo $taxonomy; ?>-pop" class="tabs-panel" style="display: none;">
-			<ul id="<?php echo $taxonomy; ?>checklist-pop" class="categorychecklist form-no-clear" >
-				<?php $popular_ids = wp_popular_terms_checklist($taxonomy); ?>
+		<div id="<?php echo $tax_name; ?>-pop" class="tabs-panel" style="display: none;">
+			<ul id="<?php echo $tax_name; ?>checklist-pop" class="categorychecklist form-no-clear" >
+				<?php $popular_ids = wp_popular_terms_checklist( $tax_name ); ?>
 			</ul>
 		</div>
 
-		<div id="<?php echo $taxonomy; ?>-all" class="tabs-panel">
+		<div id="<?php echo $tax_name; ?>-all" class="tabs-panel">
 			<?php
-            $name = ( $taxonomy == 'category' ) ? 'post_category' : 'tax_input[' . $taxonomy . ']';
+            $name = ( $tax_name == 'category' ) ? 'post_category' : 'tax_input[' . $tax_name . ']';
             echo "<input type='hidden' name='{$name}[]' value='0' />"; // Allows for an empty term set to be sent. 0 is an invalid Term ID and will be ignored by empty() checks.
             ?>
-			<ul id="<?php echo $taxonomy; ?>checklist" data-wp-lists="list:<?php echo $taxonomy?>" class="categorychecklist form-no-clear">
-				<?php wp_terms_checklist($post->ID, array( 'taxonomy' => $taxonomy, 'popular_cats' => $popular_ids ) ) ?>
+			<ul id="<?php echo $tax_name; ?>checklist" data-wp-lists="list:<?php echo $tax_name; ?>" class="categorychecklist form-no-clear">
+				<?php wp_terms_checklist( $post->ID, array( 'taxonomy' => $tax_name, 'popular_cats' => $popular_ids ) ); ?>
 			</ul>
 		</div>
-	<?php if ( current_user_can($tax->cap->edit_terms) ) : ?>
-			<div id="<?php echo $taxonomy; ?>-adder" class="wp-hidden-children">
+	<?php if ( current_user_can( $taxonomy->cap->edit_terms ) ) : ?>
+			<div id="<?php echo $tax_name; ?>-adder" class="wp-hidden-children">
 				<h4>
-					<a id="<?php echo $taxonomy; ?>-add-toggle" href="#<?php echo $taxonomy; ?>-add" class="hide-if-no-js">
+					<a id="<?php echo $tax_name; ?>-add-toggle" href="#<?php echo $tax_name; ?>-add" class="hide-if-no-js">
 						<?php
 							/* translators: %s: add new taxonomy label */
-							printf( __( '+ %s' ), $tax->labels->add_new_item );
+							printf( __( '+ %s' ), $taxonomy->labels->add_new_item );
 						?>
 					</a>
 				</h4>
-				<p id="<?php echo $taxonomy; ?>-add" class="category-add wp-hidden-child">
-					<label class="screen-reader-text" for="new<?php echo $taxonomy; ?>"><?php echo $tax->labels->add_new_item; ?></label>
-					<input type="text" name="new<?php echo $taxonomy; ?>" id="new<?php echo $taxonomy; ?>" class="form-required form-input-tip" value="<?php echo esc_attr( $tax->labels->new_item_name ); ?>" aria-required="true"/>
-					<label class="screen-reader-text" for="new<?php echo $taxonomy; ?>_parent">
-						<?php echo $tax->labels->parent_item_colon; ?>
+				<p id="<?php echo $tax_name; ?>-add" class="category-add wp-hidden-child">
+					<label class="screen-reader-text" for="new<?php echo $tax_name; ?>"><?php echo $taxonomy->labels->add_new_item; ?></label>
+					<input type="text" name="new<?php echo $tax_name; ?>" id="new<?php echo $tax_name; ?>" class="form-required form-input-tip" value="<?php echo esc_attr( $taxonomy->labels->new_item_name ); ?>" aria-required="true"/>
+					<label class="screen-reader-text" for="new<?php echo $tax_name; ?>_parent">
+						<?php echo $taxonomy->labels->parent_item_colon; ?>
 					</label>
-					<?php wp_dropdown_categories( array( 'taxonomy' => $taxonomy, 'hide_empty' => 0, 'name' => 'new'.$taxonomy.'_parent', 'orderby' => 'name', 'hierarchical' => 1, 'show_option_none' => '&mdash; ' . $tax->labels->parent_item . ' &mdash;' ) ); ?>
-					<input type="button" id="<?php echo $taxonomy; ?>-add-submit" data-wp-lists="add:<?php echo $taxonomy ?>checklist:<?php echo $taxonomy ?>-add" class="button category-add-submit" value="<?php echo esc_attr( $tax->labels->add_new_item ); ?>" />
-					<?php wp_nonce_field( 'add-'.$taxonomy, '_ajax_nonce-add-'.$taxonomy, false ); ?>
-					<span id="<?php echo $taxonomy; ?>-ajax-response"></span>
+					<?php wp_dropdown_categories( array( 'taxonomy' => $tax_name, 'hide_empty' => 0, 'name' => 'new' . $tax_name . '_parent', 'orderby' => 'name', 'hierarchical' => 1, 'show_option_none' => '&mdash; ' . $taxonomy->labels->parent_item . ' &mdash;' ) ); ?>
+					<input type="button" id="<?php echo $tax_name; ?>-add-submit" data-wp-lists="add:<?php echo $tax_name; ?>checklist:<?php echo $tax_name; ?>-add" class="button category-add-submit" value="<?php echo esc_attr( $taxonomy->labels->add_new_item ); ?>" />
+					<?php wp_nonce_field( 'add-' . $tax_name, '_ajax_nonce-add-' . $tax_name, false ); ?>
+					<span id="<?php echo $tax_name; ?>-ajax-response"></span>
 				</p>
 			</div>
 		<?php endif; ?>