Notification for Telegram <= 3.5.1 - Missing Authorization to Authenticated (Subscriber+) Cron Modification via nftb_cron_action_set AJAX Action

The Notification for Telegram plugin for WordPress is vulnerable to authorization bypass in all versions up to, and including, 3.5.1. This is due to the plugin not properly verifying that a user is authorized to perform an action. This makes it possible for authenticated attackers, with subscriber-level access and above, to create, modify, or reschedule the nftb_cron_hook WordPress cron event, enabling unauthorized manipulation of the plugin's background task scheduling logic.