GHSA-P2CH-C2C3-4XM5

Winter: CSRF through AJAX handler names reachable as backend page actions

Affected versions of Winter CMS allow a backend AJAX handler to be invoked by a plain top-level GET navigation with no CSRF token. Backend\Classes\Controller::actionExists() accepted any public method on a controller as a page action, so handler-shaped names were never reserved from URL dispatch: an authenticated and authorized request to /backend/system/eventlogs/index_onEmptyLog reached the handler of the same name and truncated the system event log. Backend paths are routed through Route::any, and CSRF validation is skipped for HEAD, GET and OPTIONS requests.

The default SameSite=Lax session cookie is sent on top-level cross-site navigation, so a link on an attacker-controlled page is sufficient, no form, no script and no token. Handler arguments are taken from URL path segments, so the attacker also chooses the target record. Affected handlers across the backend, cms and system modules cover log truncation, resetting settings to their defaults, altering backend user state, and deleting CMS templates. None of them disclose data to the attacker or write attacker-controlled content, so the impact is destructive and state-changing rather than confidential.

To actively exploit this issue, an attacker would need no account of their own, but would need an authenticated backend user holding the relevant permission to follow an attacker-supplied link. The permissions guarding the affected handlers, system.access_logs included, are by default assigned only to the built-in Developer role.

A victim's authenticated browser session is used to submit forged requests to an application that cannot distinguish them from legitimate ones. Typical impact: state-changing actions performed as the victim without their consent.

GHSA-P2CH-C2C3-4XM5 has a CVSS score of 6.1 (Medium). The vector is network-reachable, high privileges required, and user interaction required. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (1.2.14); upgrading removes the vulnerable code path.

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Page-action dispatch is now restricted to all-lowercase method names, which reserves handler-shaped names (onFoo, index_onFoo) from being reached by URL. AJAX dispatch is unchanged: handlers continue to work over POST with the X-WINTER-REQUEST-HANDLER header exactly as before, and need no changes.

IMPORTANT: This fix includes a breaking change to backend action routing. A public controller method used as a page action must now be named in lowercase, coming_soon() rather than comingSoon(), and dashed URLs are normalised to snake_case, so /coming-soon now resolves to coming_soon() instead of comingSoon(). Plugins with a camelCase page action should rename the method and its view file to match; the published URL does not need to change. Core is unaffected, and a survey of the plugin ecosystem found the change affects only a small number of plugins.

This security issue has been fixed in v1.2.14.

1. What is GHSA-P2CH-C2C3-4XM5? GHSA-P2CH-C2C3-4XM5 is a medium-severity cross-site request forgery (CSRF) vulnerability in winter/wn-backend-module (composer), affecting versions >= 1.0.319, < 1.2.14. It is fixed in 1.2.14. A victim's authenticated browser session is used to submit forged requests to an application that cannot distinguish them from legitimate ones.
2. How severe is GHSA-P2CH-C2C3-4XM5? GHSA-P2CH-C2C3-4XM5 has a CVSS score of 6.1 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of winter/wn-backend-module are affected by GHSA-P2CH-C2C3-4XM5? winter/wn-backend-module (composer) versions >= 1.0.319, < 1.2.14 is affected.
4. Is there a fix for GHSA-P2CH-C2C3-4XM5? Yes. GHSA-P2CH-C2C3-4XM5 is fixed in 1.2.14. Upgrade to this version or later.
5. Is GHSA-P2CH-C2C3-4XM5 exploitable, and should I be worried? Whether GHSA-P2CH-C2C3-4XM5 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether GHSA-P2CH-C2C3-4XM5 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix GHSA-P2CH-C2C3-4XM5? Upgrade winter/wn-backend-module to 1.2.14 or later.

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