Index: wp-includes/customize/class-wp-customize-date-time-control.php
===================================================================
--- wp-includes/customize/class-wp-customize-date-time-control.php	(revision 54300)
+++ wp-includes/customize/class-wp-customize-date-time-control.php	(working copy)
@@ -173,7 +173,7 @@
 								<option value="pm"><?php esc_html_e( 'PM' ); ?></option>
 							</select>
 						<# } #>
-						<p><?php echo $timezone_info['description']; ?></p>
+						<p><?php echo esc_html($timezone_info['description']); ?></p>
 					</div>
 				</fieldset>
 			<# } #>