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CVE-2026-52766 – Unauthenticated Arbitrary Page Deletion – YesWiki < 4.6.6

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Summary

CVE-2026-52766 is a critical missing-authorization vulnerability in YesWiki, a PHP-based wiki platform, that allows an unauthenticated or low-privileged attacker to permanently delete arbitrary wiki pages, including the front page and admin pages. The flaw resides in the {{erasespamedcomments}} wiki action, which processes page-deletion requests without any authorization or ownership checks. It carries a CVSS score of 9.1 (Critical) and affects all YesWiki versions prior to 4.6.6.

Technical details

  • Root cause: actions/EraseSpamedCommentsAction.php accepts a suppr[] array of page names from a POST request and passes them directly to PageManager::deleteOrphaned() without verifying that the caller has deletion rights.
  • PageManager::deleteOrphaned(), despite its name, performs no orphan check — it issues unconditional DELETE statements against the pages, links, acls, triples, referrers, and tags database tables.
  • Trigger conditions: On a default YesWiki installation, default_write_acl='*' grants everyone, including anonymous visitors, permission to create a page. An attacker embeds {{erasespamedcomments}} on a page they create, then submits a crafted POST request containing target page names in suppr[].
  • Attack vector: Network-based, requires no authentication and no user interaction, exploitable via a two-step process (create trigger page, then submit deletion request).
  • Impact: Permanent deletion of any wiki page, including the site’s front page and pages owned by other users, resulting in high integrity and availability impact.
  • Weaknesses: CWE-862 (Missing Authorization) and CWE-276 (Incorrect Default Permissions).

Affected software

  • YesWiki (yeswiki/yeswiki) versions prior to 4.6.6

Severity

  • CVSS v3.1 Base Score: 9.1 (Critical)
  • Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H

Mitigation and recommended actions

  • Immediate: Upgrade to YesWiki version 4.6.6 or later, which adds an admin authorization guard at the entry point of EraseSpamedCommentsAction::run() before any POST data is processed.
  • If unable to patch immediately: Restrict the erasespamedcomments action by adding it to the site’s permissions configuration map and setting its ACL so that only admins (%) can invoke it.

How IONIX identifies potentially affected assets

IONIX matches the following signals against data already collected when it crawled the asset; identifying the technology sends no request beyond that crawl.

  • HTTP response header link: YesWiki-
  • Raw HTTP response body: yeswiki.net

References

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