GHSA-3h6j-9x8m-rg3g: J0k3r/graby Cross-Site Scripting Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-3h6j-9x8m-rg3g",
  "modified" : "2026-03-31T23:12:36Z",
  "published" : "2026-03-31T23:12:36Z",
  "aliases" : [ ],
  "summary" : "Graby has stored XSS via iframe srcdoc Attribute in htmLawed Sanitization Config",
  "details" : "## Summary\n\nGraby's `cleanupXss()` function configures htmLawed with conflicting settings: `safe=1` (which removes `<iframe>`) combined with `'elements' => '*+iframe-meta'` (which re-enables `<iframe>`). htmLawed does not sanitize the `srcdoc` attribute, allowing injection of arbitrary JavaScript that executes when the content is rendered via `|raw` in templates.\n\n## Root Cause\n\n**`src/Graby.php` lines 1038-1048:**\n```php\nhtmLawed($html, [\n    'safe' => 1,                    // removes <iframe>\n    'elements' => '*+iframe-meta',  // re-adds <iframe>, overrides safe=1\n    'deny_attribute' => 'style',    // srcdoc is NOT denied\n]);\n```\n\nThe `safe=1` and `+iframe` combination is a conflict: `safe` mode is designed to strip dangerous elements, but the elements override re-enables `<iframe>` without also blocking the dangerous `srcdoc` attribute.\n\n## Proof of Concept\n\nInput to `cleanupXss()`:\n```html\n<iframe srcdoc=\"&lt;script&gt;alert(document.domain)&lt;/script&gt;\"></iframe>\n```\n\nOutput (unchanged — htmLawed passes it through):\n```html\n<iframe srcdoc=\"&lt;script&gt;alert(document.domain)&lt;/script&gt;\"></iframe>\n```\n\nWhen rendered via `{{ content|raw }}` in a template, `srcdoc` executes in an `about:srcdoc` frame with the same origin as the page. **Confirmed via Puppeteer/Chromium headless: `alert(document.domain)` fires.**\n\nValidated on Wallabag (which uses Graby) via Docker: entry created via API with iframe-only content body triggers Readability failure → falls through to `cleanupXss()` path.\n\n## Impact\n\n- Stored XSS in any application rendering Graby-sanitized content via `|raw`\n- In Wallabag: affects both authenticated views and public share pages (unauthenticated)\n- No CSP headers in default Wallabag config — no secondary mitigation\n\n## Suggested Fix\n\nEither remove `+iframe` from the elements config to keep iframes blocked:\n```php\n'elements' => '*-iframe-meta',\n```\n\nOr explicitly deny the `srcdoc` attribute:\n```php\n'deny_attribute' => 'style srcdoc',\n```\n\n## Credit\n\nDiscovered by @tikket1, 2026-03-25. Redirected from wallabag/wallabag advisory by @j0k3r.",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N/E:P"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Packagist",
      "name" : "j0k3r/graby"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "2.5.1"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 2.5.0"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/j0k3r/graby/security/advisories/GHSA-3h6j-9x8m-rg3g"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/j0k3r/graby/commit/0295d828822f7a59c5751a8199973a4f965a99b0"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/j0k3r/graby"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/j0k3r/graby/releases/tag/2.5.1"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-79" ],
    "severity" : "LOW",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-03-31T23:12:36Z",
    "nvd_published_at" : null
  }
}