Ticket #51379: 51379.2.diff

src/wp-includes/user.php

@@ -1623 +1623 @@
 function email_exists( $email ) {
         $user = get_user_by( 'email', $email );
         if ( $user ) {
-                return $user->ID;
+                $user_id = $user->ID;
+        } else {
+                $user_id = false;
         }
-        return false;
+
+        /**
+         * Filters whether the given email exists or not.
+         *
+         * @since 5.6.0
+         *
+         * @param int|false $user_id The user's ID on success, and false on failure.
+         * @param string    $email   Email.
+         */
+        return apply_filters( 'email_exists', $user_id, $email );
 }
 
 /**