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

• >= 1.0.319, < 1.2.14

### 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 con

GitHub Advisory Database

• ECOSYSTEM: introduced 1.0.319; fixed 1.2.14

### 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 con

GitHub Advisory Database via OSV