CVE-2026-115483: 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 attachentryfiles() function. This is due to the function attaching any entry field value whose meta key matches /signature/ to the notification email after only a fileexists() 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.