CVE-2026-4350: Perfmatters <= 2.5.9.1 - Authenticated (Subscriber+) Arbitrary File Deletion via 'delete' Parameter

The Perfmatters plugin for WordPress is vulnerable to arbitrary file deletion via path traversal in all versions up to, and including, 2.5.9.1. This is due to the `PMCS::action_handler()` method processing the `$_GET['delete']` parameter without any sanitization, authorization check, or nonce verification. The unsanitized filename is concatenated with the storage directory path and passed to `unlink()`. This makes it possible for authenticated attackers, with Subscriber-level access and above, to delete arbitrary files on the server by using `../` path traversal sequences, including `wp-config.php` which would force WordPress into the installation wizard and allow full site takeover.