Shield is an authentication and authorization framework for CodeIgniter 4. This vulnerability may allow [SameSite Attackers](https://canitakeyoursubdomain.name/) to bypass the [CodeIgniter4 CSRF protection](https://codeigniter4.github.io/userguide/libraries/security.html) mechanism with CodeIgniter Shield. For this attack to succeed, the attacker must have direct (or indirect, e.g., XSS) control over a subdomain site (e.g., `https://a.example.com/`) of the target site (e.g., `http://example.com/`). Upgrade to **CodeIgniter v4.2.3 or later** and **Shield v1.0.0-beta.2 or later**. As a workaround: set `Config\Security::$csrfProtection` to `'session,'`remove old session data right after login (immediately after ID and password match) and regenerate CSRF token right after login (immediately after ID and password match)

Affected: Packagist: codeigniter4/shield

### Impact This vulnerability may allow [SameSite Attackers](https://canitakeyoursubdomain.name/) to bypass the [CodeIgniter4 CSRF protection](https://codeigniter4.github.io/userguide/libraries/security.html) mechanism with CodeIgniter Shield.

For this attack to succeed, the attacker must have direct (or indirect, e.g., XSS) control over a subdomain site (e.g., `https://a.example.com/`) of the target site (e.g., `http://example.com/`).

This vulnerability exists whether `Config\Security::$csrfProtection` is `'cookie'` or `'session'`. It is also exploitable whether `Config\Security::$regenerate` is `true` or `false`.

### Patches Upgrade to **CodeIgniter v4.2.3 or later** and **Shield v1.0.0-beta.2 or later**.

### Workarounds Do all of the following: - set `Config\Security::$csrfProtection` to `'session'` - remove old session data right after login (immediately after ID and password match) - regenerate CSRF token right after login (immediately after ID and password match)

### References - [CodeIgniter4 CSRF Protection](https://codeigniter4.github.io/userguide/libraries/security.html) - [SameSite Attacks](https://canitakeyoursubdomain.name/) - [SameSite Cookies](https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Set-Cookie/SameSite) - [The great SameSite confusion](https://jub0bs.com/posts/2021-01-29-great-samesite-confusion/)

### For more information If you have any questions or comments about this advisory: * Open an issue or discussion in [codeigniter4/shield](ht…