Electron is a framework for writing cross-platform desktop applications using JavaScript, HTML and CSS. Prior to 39.8.9, 40.9.2, 41.2.2, and 42.0.0-beta.5, apps that expose Promise-returning functions to web content via contextBridge may be vulnerable to a context isolation bypass. Untrusted web content could obtain access to the isolated preload world and, through it, every capability the preload script has. In renderers without a sandbox, or with nodeIntegration enabled, this may escalate to Node.js access. Apps are affected if they expose Promise-returning functions via contextBridge, the standard pattern for wrapping ipcRenderer.invoke, in windows that load untrusted content. This issue is fixed in versions 39.8.9, 40.9.2, 41.2.2, and 42.0.0-beta.5.