Electron: Use-after-free in WebContents fullscreen, pointer-lock, and keyboard-lock permission callbacks

### Impact Apps that register an asynchronous `session.setPermissionRequestHandler()` may be vulnerable to a use-after-free when handling fullscreen, pointer-lock, or keyboard-lock permission requests. If the requesting frame navigates or the window closes while the permission handler is pending, invoking the stored callback dereferences freed memory, which may lead to a crash or memory corruption. Apps that do not set a permission request handler, or whose handler responds synchronously, are not affected. ### Workarounds Respond to permission requests synchronously, or deny fullscreen, pointer-lock, and keyboard-lock requests if an asynchronous flow is required. ### Fixed Versions * `41.0.0-beta.8` * `40.7.0` * `39.8.0` * `38.8.6` ### For more information If there are any questions or comments about this advisory, please email [security@electronjs.org](mailto:security@electronjs.org)