A number of keys that have only been used once are referred to as once. Nonces are used by WordPress to safeguard URLs and forms against malicious hacking attempts. When you trash or remove a comment on the comment moderation screen, for example, WordPress adds a nonce key to the URL like this:
A verification check is performed when a URL with a nonce key is run. If this check fails, WordPress responds with a 403 Forbidden error message with the message “Are you sure you want to do this?”
‘Are you sure this is what you want to do?’ When nonce verification fails, an error message may show on any screen.
The most typical source of this issue is a badly coded plugin or theme that fails to check the nonce. To resolve this problem, a user can disable all plugins and then reactivate them one by one to determine which one is causing the error.
In the case of themes, reverting to the default theme and then attempting to duplicate the error may reveal that the prior theme in use was the source of the problem.
Nonce provides a security system for WordPress functions and features that conduct particular operations using the query string in the URL. NONCE SALT and NONCE KEY are used by WordPress to produce unique nonces. These nonce salts and keys, as well as other unique keys, are saved in the wp-config.php file and are exclusive to each WordPress installation.