CVE-2026-43940: Electerm runWidget has a path traversal that leads to arbitrary code execution

The runWidget function in src/app/widgets/load-widget.js constructs a file path by directly concatenating user‑supplied widget identifiers without any sanitisation:

const file = `widget-${widgetId}.js`
const widget = require(path.join(__dirname, file))

Because runWidget is exposed to the renderer process via an asynchronous IPC handler with no input validation, an attacker who achieves JavaScript execution inside the renderer (for example, through a malicious plugin or a cross‑site scripting flaw in the built‑in webview) can abuse a path traversal (../) to load and execute an arbitrary JavaScript file anywhere on the victim’s filesystem. This gives the attacker local code execution with the full privileges of the electerm process, leading to complete system compromise.