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CVE-2026-104450 – ACL Bypass Leading to Stored XSS – YesWiki before 4.6.7

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Summary

CVE-2026-104450 is a missing-authorization vulnerability in YesWiki, an open-source PHP wiki engine, that allows unauthenticated attackers to bypass page write-ACL protections and inject stored cross-site scripting (XSS) payloads into arbitrary wiki pages. The flaw resides in the pointimage action and affects all YesWiki versions prior to 4.6.7. It carries a CVSS v4.0 base score of 8.2 (High).

Technical details

  • Root cause: The pointimage action, implemented in tools/attach/actions/pointimage.php, saves attacker-supplied content to a target page without performing the write ACL check that normally restricts who can edit that page.
  • Trigger conditions: Any page that renders the {{pointimage}} wiki syntax exposes the vulnerable action, so no special configuration is required beyond the default use of this common attachment/annotation feature.
  • Attack vector: An unauthenticated remote attacker sends a crafted POST request to the pointimage action containing pagetag, title, and description parameters pointing at a page the attacker does not otherwise have permission to edit.
  • Impact: Because the write ACL check is bypassed, raw HTML/JavaScript supplied in these fields is appended to the targeted page, including pages whose ACLs are meant to restrict editing. This results in persistent (stored) XSS that executes in the browsers of any user who later views the page, including administrators — enabling session hijacking, credential theft, or further compromise of the wiki.

Affected software

  • YesWiki versions prior to 4.6.7 (all versions, version 0 up to but excluding 4.6.7)
  • Fixed in YesWiki 4.6.7

Severity

  • CVSS v4.0: 8.2 (High) — CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:L/SI:L/SA:N
  • CVSS v3.1: 6.5 (Medium) — CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:H/A:N

Mitigation and recommended actions

  • Immediate: Upgrade YesWiki to version 4.6.7 or later, which restores the write ACL check in the pointimage action.
  • If no patch can be applied immediately: Restrict or disable use of the {{pointimage}} action on pages where untrusted users can submit input, and consider placing the wiki behind a web application firewall configured to block unauthenticated POST requests to the pointimage action endpoint until the upgrade can be completed. Review existing pages for injected HTML/JavaScript content that may already have been planted via this flaw.

References

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