WP 22321 bug call stack

( ! ) Fatal error: Class 'DOMDocument' not found in /var/www/vhosts/[redacted]/httpdocs/wp/wordpress/wp-includes/SimplePie/Sanitize.php on line 250
Call Stack
#	Time	Memory	Function	Location
1	0.0007	666904	{main}( )	../admin-ajax.php:0
2	0.2153	38413544	do_action( )	../admin-ajax.php:70
3	0.2154	38415216	call_user_func_array ( )	../plugin.php:406
4	0.2154	38415248	wp_ajax_dashboard_widgets( )	../plugin.php:406
5	0.2177	39118624	wp_dashboard_plugins( )	../ajax-actions.php:204
6	0.2177	39119440	wp_dashboard_cached_rss_widget( )	../dashboard.php:908
7	0.2186	39162528	call_user_func_array ( )	../dashboard.php:1029
8	0.2187	39162952	wp_dashboard_plugins_output( )	../dashboard.php:1029
9	0.2505	44232408	SimplePie_Item->get_description( )	../dashboard.php:964
10	0.2506	44232504	SimplePie_Item->sanitize( )	../Item.php:339
11	0.2506	44232504	SimplePie->sanitize( )	../Item.php:182
12	0.2506	44232504	SimplePie_Sanitize->sanitize( )	../class-simplepie.php:2026