WP Captcha PRO <= 5.38 - Missing Authorization to Authenticated (Subscriber+) Arbitrary File Upload

The WP Captcha PRO (the premium version of the Advanced Google reCAPTCHA plugin, both have the same slug) plugin for WordPress is vulnerable to arbitrary file upload in all versions up to, and including, 5.38. This is due to a capability check in the save_ajax() function of the licensing module, combined with unrestricted file extraction in sync_cloud_protection(). This makes it possible for authenticated attackers, with Subscriber-level access and above, to upload arbitrary files including PHP webshells to the server by injecting a malicious cloud_protection_url into the license meta, which the plugin then downloads and extracts without file type validation into a web-accessible uploads directory. This can be used for remote code execution. Note: The vulnerability can only be exploited with a remote URL if "allow_url_fopen" is enabled in the php.ini config.