If you notice this file under your WordPress root directory, that’s a sign your website is infected with malware. Perform a backup, including the web files and database. And proceed with a professional malware cleanup, or do it yourself following one of our guides.
Try our Free site check.
At this point, most likely, the index.php file is also injected with malicious code. And several Javascript files may be affected too. So a thorough site check & cleanup is recommended.
wp-reset.php malicious code