GHSA-p2ch-c2c3-4xm5

### Impact 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. ### Patches 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