CVE-2026-48806 Twig: Sandbox `__toString()` policy bypass via dynamic mapping keys

Twig is a template language for PHP. Prior to 3.27.0, ArrayExpression does not guard dynamic mapping keys that are coerced to strings, allowing PHP to invoke toString on a Stringable object used as a mapping key without calling SandboxExtension::ensureToStringAllowed. This issue is fixed in versi...