Compromised child renderer processes could obtain IPC access without nodeIntegrationInSubFrames being enabled

Electron is a framework for writing cross-platform desktop applications using JavaScript (JS), HTML, and CSS. A vulnerability in versions prior to 18.0.0-beta.6, 17.2.0, 16.2.6, and 15.5.5 allows a renderer with JS execution to obtain access to a new renderer process with `nodeIntegrationInSubFrames` enabled which in turn allows effective access to `ipcRenderer`. The `nodeIntegrationInSubFrames` option does not implicitly grant Node.js access. Rather, it depends on the existing sandbox setting. If an application is sandboxed, then `nodeIntegrationInSubFrames` just gives access to the sandboxed renderer APIs, which include `ipcRenderer`. If the application then additionally exposes IPC messages without IPC `senderFrame` validation that perform privileged actions or return confidential data this access to `ipcRenderer` can in turn compromise your application / user even with the sandbox enabled. Electron versions 18.0.0-beta.6, 17.2.0, 16.2.6, and 15.5.5 contain a fix for this issue. As a workaround, ensure that all IPC message handlers appropriately validate `senderFrame`.