Ticket #33475: 33475.diff

src/wp-includes/cron.php

@@ -21 +21 @@
  * @return void|false
  */
 function wp_schedule_single_event( $timestamp, $hook, $args = array()) {
+        // check timestamp positive number
+        if ( ! is_numeric( $timestamp ) || $timestamp <= 0 ){
+                return ;
+        }
+
         // don't schedule a duplicate if there's already an identical event due within 10 minutes of it
         $next = wp_next_scheduled($hook, $args);
         if ( $next && abs( $next - $timestamp ) <= 10 * MINUTE_IN_SECONDS ) {