{
  "affected": [
    {
      "package": {
        "ecosystem": "Packagist",
        "name": "craftcms/cms"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "5.0.0-RC1"
            },
            {
              "fixed": "5.9.21"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-50279"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-285"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-07-02T18:45:28Z",
    "nvd_published_at": "2026-07-02T00:16:44Z",
    "severity": "HIGH"
  },
  "details": "### Summary\n\n`EntriesController::actionSaveEntry()` performs entry-edit permission checks before request-controlled author changes are applied to the model. The subsequent author mutation path accepts attacker-supplied `authors` / `author` parameters and allows the change when the current user is one of the old authors. Because the controller does not re-run authorization after mutating the author list, a low-privileged user can reassign an entry\u2019s authorship to another user without holding the dedicated peer-author-change permission.\n\n### Details\nThe control flow begins in [EntriesController.php](/D:/files/projects/cms-5.9.19/cms-5.9.19/src/controllers/EntriesController.php):249. `actionSaveEntry()` loads the entry and enforces edit permissions before calling `_populateEntryModel()`:\n\n```php\npublic function actionSaveEntry(bool $duplicate = false): ?Response\n{\n    ...\n    $entry = $this-\u003e_editableEntry($this-\u003erequest-\u003egetBodyParam(\u0027entryId\u0027), $siteId);\n    ...\n    $this-\u003eenforceEditEntryPermissions($entry, $duplicate);\n    ...\n    $this-\u003e_populateEntryModel($entry);\n    ...\n    $success = Craft::$app-\u003egetElements()-\u003esaveElement($entry);\n}\n```\n\nThe attacker-controlled source is in [EntriesController.php](/D:/files/projects/cms-5.9.19/cms-5.9.19/src/controllers/EntriesController.php):588:\n\n```php\n$entry-\u003esetAttributesFromRequest(array_filter([\n    \u0027authorIds\u0027 =\u003e $this-\u003erequest-\u003egetBodyParam(\u0027authors\u0027) ??\n        $this-\u003erequest-\u003egetBodyParam(\u0027author\u0027) ??\n        $entry-\u003egetAuthorId() ??\n        static::currentUser()-\u003eid,\n]));\n```\n\n`Entry::setAttributesFromRequest()` in [Entry.php](/D:/files/projects/cms-5.9.19/cms-5.9.19/src/elements/Entry.php):1124 extracts the new author IDs and applies them if `canChangeAuthor()` returns true:\n\n```php\nif (\n    ($authorIds !== null || $authorId !== null) \u0026\u0026\n    $this-\u003ecanChangeAuthor()\n) {\n    $this-\u003e_oldAuthorIds = $oldAuthorIds;\n    $this-\u003esetAuthorIds($authorIds);\n}\n```\n\n`canChangeAuthor()` at [Entry.php](/D:/files/projects/cms-5.9.19/cms-5.9.19/src/elements/Entry.php):2789 allows the author change when the current user can view peer entries and is already one of the existing authors:\n\n```php\nreturn (\n    empty($authorIds) ||\n    in_array($user-\u003eid, $authorIds) ||\n    $user-\u003ecan(\"changeAuthorForPeerEntries:$section-\u003euid\")\n);\n```\n\nAfter the author list is mutated, the controller does not re-check authorization. \n\nThis closes the exploit chain:\n\n1. External source: authenticated request to `entries/save-entry` with attacker-controlled `authors[]`.\n2. Trust boundary failure: authorization is checked on the pre-mutation entry state, not on the post-mutation author assignment.\n3. Privileged sink: the author relationship is rewritten in persistent storage.\n\nPreconditions derived from the source:\n\n1. The attacker is authenticated and can edit entry `345`.\n2. The attacker is among the existing authors of entry `345`, or otherwise satisfies `canChangeAuthor()` through the old author set.\n3. The attacker has `viewPeerEntries` for the section.\n4. User ID `1` exists and can be assigned as an author in that section.\n\nResult:\n\n1. `enforceEditEntryPermissions()` succeeds on the original entry state.\n2. `_populateEntryModel()` reads `authors[]=1` from the request body.\n3. `setAttributesFromRequest()` updates `authorIds` because `canChangeAuthor()` is evaluated against the old authorship state.\n4. `saveElement()` persists the change and `_saveAuthors()` rewrites the entry-author relation.\n5. Entry `345` now appears authored by user `1`.\n\n### Impact\n\nThis allows low-privileged users to falsify content ownership and alter the authorship of entries without having the dedicated author-management permission. The impact includes corrupted audit trails, misleading notifications, broken approval workflows, and unauthorized reassignment of content responsibility.",
  "id": "GHSA-qq2c-2q8j-jh27",
  "modified": "2026-07-02T18:45:28Z",
  "published": "2026-07-02T18:45:28Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/craftcms/cms/security/advisories/GHSA-qq2c-2q8j-jh27"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-50279"
    },
    {
      "type": "WEB",
      "url": "https://github.com/craftcms/cms/commit/9cc493be8b414d7116c7f2bc2a6d0926e73f1248"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/craftcms/cms"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "Craft CMS: Authorship spoofing in `entries/save-entry` via pre-check/post-mutation authorization gap"
}