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CVE-2026-18110 is an improper-authorization vulnerability in Concrete CMS 9.0.0 through 9.5.2 affecting the user-selector autocomplete functionality used by the Preview as User panel and related components. The functionality validates a CSRF-style token that is bound to selector display options rather than the requesting user's identity or permissions. Because anonymous visitors can obtain the token, an unauthenticated attacker can submit an empty search, which acts as a match-all query, and paginate through backend user records.
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1 valid exploit after Mallory filtered fakes, detection scripts, and README-only repos.
The repository contains a standalone Python 3 proof of concept, a Nuclei template, and supporting documentation for CVE-2026-18110. It targets a missing authorization check in Concrete CMS's Preview As User/user-autocomplete workflow. The Python script accepts one target URL, disables TLS certificate verification, fetches the unauthenticated Preview As User panel, regex-extracts the access-token attribute from a concrete-user-select element, and POSTs that token to the autocomplete route. It parses and prints returned IDs plus primary and secondary labels. The Nuclei template implements the same two-request chain and extracts the token, label format, and avatar setting from the first response before validating user-record fields in the second. This is an operational unauthenticated enumeration exploit rather than only a detector: successful execution obtains user-directory data, although it does not execute commands or establish access beyond information disclosure.
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4 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
An unauthenticated missing-authorization vulnerability in Concrete CMS endpoints that exposes an access token and permits retrieval of the full user list, including usernames and email addresses.
An unauthenticated account-enumeration and information-disclosure vulnerability in Concrete CMS 9's user-selector autocomplete endpoint. The endpoint accepts a CSRF-style token that is not bound to the caller's identity or authorization, enabling enumeration of all backend users, including the super-administrator.
A high-severity missing-authorization vulnerability in Concrete CMS 9's user selector autocomplete endpoint. Anonymous users can obtain a selector access token and exploit an empty query to enumerate the full backend user directory, including administrative and super-administrator account identifiers, usernames, and email addresses. Password hashes and session material are not disclosed.
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Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.