Everest Forms <= 3.6.3 - Unauthenticated Arbitrary File Read via 'Signature' Field Meta Key Branch of attach_entry_files

The Everest Forms plugin for WordPress is vulnerable to Arbitrary File Read in all versions up to, and including, 3.6.3 via the attach_entry_files() function. This is due to the function attaching any entry field value whose meta key matches /signature_/ to the notification email after only a file_exists() check, without validating or restricting the path. This makes it possible for unauthenticated attackers to read the contents of arbitrary files on the server, such as wp-config.php, which can contain sensitive information. Successful exploitation requires a form whose email notification has the “Attach Files” setting enabled and that contains a field with a meta key matching /signature_/ (for example, a text field labelled “Signature”), with the notification routed to an attacker-supplied email address so the exfiltrated file is delivered to the attacker. Note: The Everest Forms Pro add-on is required to exploit this vulnerability, as it provides the signature field and the email file-attachment functionality (file-email-attachments) that the attack relies on.

Requests carrying this pattern arrive without a session, so nothing upstream of the firewall gets a chance to reject them: WordSec's web application firewall inspects request payloads before WordPress loads them. No patched version is recorded yet, which is the case where a filtering layer matters most, because there is nothing to update to.

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