Ticket #53296: 53296.patch

src/wp-includes/class-wp-hook.php

@@ -71 +71 @@
         * @param int      $accepted_args The number of arguments the function accepts.
         */
        public function add_filter( $hook_name, $callback, $priority, $accepted_args ) {
+
+               $hook_name = trim( $hook_name );
+
                $idx = _wp_filter_build_unique_id( $hook_name, $callback, $priority );
 
                $priority_existed = isset( $this->callbacks[ $priority ] );

src/wp-includes/plugin.php

@@ -114 +114 @@
 function add_filter( $hook_name, $callback, $priority = 10, $accepted_args = 1 ) {
        global $wp_filter;
 
+       $hook_name = trim( $hook_name );
+
        if ( ! isset( $wp_filter[ $hook_name ] ) ) {
                $wp_filter[ $hook_name ] = new WP_Hook();
        }