Grav 2.0.0-rc.1 through 2.0.21 Configuration Disclosure via print_r

Grav is a flat-file CMS. In versions 2.0.0-rc.1 through 2.0.21, the Twig content sandbox fails to restrict the dump and serialize filters (print_r, vardump, json_encode, yaml_encode, string): GravExtension::assertSandboxDumpSafe() determines sandbox state by calling SandboxExtension::isSandboxed() without a Source argument, which reports only the global sandbox flag that Grav never enables, so the guard added in GHSA-mc5q-6hpj-rp7j never executes. As a result, an authenticated user with page-edit rights can render {{ config|print_r }} in page content with Twig processing enabled and dump Grav's entire merged configuration — print_r reflects the real Config object held in a private property of the SandboxConfig facade, bypassing its path redaction — exposing plugin secrets such as SMTP credentials, API tokens, webhook secrets and cache backend passwords. Grav 1.7 is not affected because it ships no Twig content sandbox. The issue is fixed in 2.0.22, where the affected filters are registered with Twig's needs_is_sandboxed flag.