CVE-2026-56707: Grav Flex Objects Authorization Bypass Flaw

CVE-2026-56707 Overview

CVE-2026-56707 is an authorization bypass vulnerability in the Grav Flex Objects plugin, versions 1.4.0 through 1.4.7. The flex-objects shortcode renders any registered Flex collection without enforcing the authorize Access Control List (ACL) used in the admin panel. A user with page-edit access can embed the shortcode in a published page to expose sensitive collections, including user account directories. The flaw is categorized under CWE-862: Missing Authorization and carries a CVSS 4.0 score of 8.3.

Critical Impact
Low-privileged editors can render arbitrary Flex collections through published pages, disclosing user account data and other protected directory contents.

Affected Products

Grav CMS Flex Objects plugin version 1.4.0
Grav CMS Flex Objects plugin versions 1.4.1 through 1.4.6
Grav CMS Flex Objects plugin version 1.4.7

Discovery Timeline

2026-08-25 - CVE-2026-56707 published to the National Vulnerability Database (NVD)
2026-08-27 - Last updated in NVD database

Technical Details for CVE-2026-56707

Vulnerability Analysis

Grav is a flat-file content management system (CMS), and the Flex Objects plugin provides a framework for managing collections such as users, pages, and custom object types. The plugin registers a flex-objects shortcode that renders these collections inside page content. In vulnerable releases, the shortcode handler skips the authorize ACL check applied by the administrative interface. Any account permitted to author or edit pages can therefore render collections restricted to administrators.

An attacker with editor-level access places the shortcode in a page, publishes it, and reads the rendered output. Depending on the referenced collection, the response can include usernames, email addresses, roles, and other directory metadata stored in Flex objects. Because rendering happens server-side and is embedded into the published page, the exposed data can be reached by any visitor who can view that page.

Root Cause

The root cause is missing authorization enforcement in the shortcode rendering path. The admin panel invokes an authorize check before returning Flex collection data, but the shortcode implementation does not replicate that check. Trust is placed on the caller having page-edit rights rather than on the caller having permission to read the requested collection.

Attack Vector

Exploitation is network-based and requires authenticated access with page-edit privileges. No user interaction is required beyond viewing the resulting page. An authenticated editor inserts the flex-objects shortcode referencing a protected collection such as the users directory. On page render, Grav evaluates the shortcode and outputs the collection contents in the HTML response. See the GitHub Security Advisory GHSA-x929-528m-vx2m and the VulnCheck advisory for technical details.

Detection Methods for CVE-2026-56707

Indicators of Compromise

Page content or Markdown files containing the flex-objects shortcode referencing sensitive collections such as accounts, users, or other administrative Flex directories.
HTTP responses from published pages containing tabular listings of usernames, emails, or account roles that should not be public.
Recent edits to published pages authored by low-privilege editor accounts that introduce shortcode syntax.

Detection Strategies

Audit the Grav user/pages directory and stored page data for occurrences of the flex-objects shortcode, prioritizing pages authored by non-administrator accounts.
Review Grav access logs for anomalous requests to page URLs that return large or structured user data payloads.
Correlate editor login events with subsequent page publish or update actions that add shortcode content referencing protected Flex types.

Monitoring Recommendations

Alert on new or modified page files that contain the string [flex-objects or the block-form equivalent.
Monitor web server responses for unexpected disclosure patterns such as bulk email addresses or account identifiers served from public pages.
Track privilege changes and page authorship for the Grav administrative user set to detect abuse of legitimate editor accounts.

How to Mitigate CVE-2026-56707

Immediate Actions Required

Upgrade the Grav Flex Objects plugin to a version later than 1.4.7 that contains the authorize ACL fix, as documented in the vendor advisory.
Inventory all published and draft pages for existing flex-objects shortcode usage and remove instances that reference protected collections.
Rotate credentials for any accounts whose data may have been exposed through rendered user or account collections.

Patch Information

Refer to the GitHub Security Advisory GHSA-x929-528m-vx2m for the fixed release information. The patched version restores the authorize ACL check within the shortcode rendering path so that collection access requires the same permissions enforced by the admin panel.

Workarounds

Restrict page-edit privileges to trusted administrators until the plugin is upgraded, reducing the population of accounts able to insert shortcodes.
Disable or remove the Flex Objects plugin if it is not required for site operation.
Implement a content review process that inspects new page content for the flex-objects shortcode before publication.

bash

# Configuration example: locate flex-objects shortcode usage in Grav content
grep -rn "\[flex-objects" user/pages/
grep -rn "flex-objects" user/data/ user/accounts/