CVE-2026-33723: AVideo is Vulnerable to SQL Injection through Subscribe Endpoint via Unsanitized user_id Parameter

The Subscribe::save() method in objects/subscribe.php concatenates the $this->users_id property directly into an INSERT SQL query without sanitization or parameterized binding. This property originates from $_POST['user_id'] in both subscribe.json.php and subscribeNotify.json.php. An authenticated attacker can inject arbitrary SQL to extract sensitive data from any database table, including password hashes, API keys, and encryption salts.