CVE-2026-8340: Concrete CMS is vulnerable to CSRF via Backend\File::approveVersion

May 26, 2026 (updated June 29, 2026)

Concrete CMS 9.5.0 and below is vulnerable to CSRF via Backend\File::approveVersion. Victim with edit_file_contents permission is CSRF’d into publishing an attacker-chosen previously-uploaded version (downgrade to an older version of a file, or activation of a co-editor’s unpublished version). Thanks Winston Crooker for reporting.

References

documentation.concretecms.org/9-x/developers/introduction/version-history/951-release-notes
github.com/advisories/GHSA-xjg6-5v39-v7fc
nvd.nist.gov/vuln/detail/CVE-2026-8340

Code Behaviors & Features

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