diff --git a/src/wp-includes/kses.php b/src/wp-includes/kses.php
index 8722176718415..663e34a66e389 100644
--- a/src/wp-includes/kses.php
+++ b/src/wp-includes/kses.php
@@ -2469,6 +2469,8 @@ function safecss_filter_attr( $css, $deprecated = '' ) {
 
 		'list-style',
 		'list-style-image',
+
+		'filter',
 	);
 
 	/*