GenerateBlocks <= 2.1.2 - Authenticated (Contributor+) Information Exposure via Metadata

Summary

The GenerateBlocks plugin for WordPress is vulnerable to information exposure due to missing object-level authorization checks in versions up to, and including, 2.1.2. This is due to the plugin registering multiple REST API routes under `generateblocks/v1/meta/` that gate access with `current_user_can('edit_posts')`, which is granted to low-privileged roles such as Contributor. The handlers accept arbitrary entity IDs (user IDs, post IDs, etc.) and meta keys, returning any requested metadata with only a short blacklist of password-like keys for protection. There is no object-level authorization ensuring the caller is requesting only their own data, and there is no allowlist of safe keys. This makes it possible for authenticated attackers, with Contributor-level access and above, to exfiltrate personally identifiable information (PII) and other sensitive profile data of administrator accounts or any other users by directly querying user meta keys via the exposed endpoints via the `get_user_meta_rest` function. In typical WordPress + WooCommerce setups, this includes names, email, phone, and address fields that WooCommerce stores in user meta, enabling targeted phishing, account takeover pretexting, and privacy breaches.