fkie_cve-2026-77394

OpenC3 COSMOS provides the functionality needed to send commands to and receive data from one or more embedded systems. From 5.0.6 until 7.3.0, an authenticated actor with system_set permission can store a shared screen through POST /openc3-api/screen whose BUTTON widget action is evaluated by openc3-cosmos-init/plugins/packages/openc3-vue-common/src/widgets/ButtonWidget.vue in another operator's browser session when the button is activated. The stored script runs in the COSMOS origin and can read localStorage.openc3Token, allowing theft of the victim's bearer token, account takeover, and actions with the victim's privileges. The permissive content security policy contributes to execution but is not the primary root cause. This issue is fixed in version 7.3.0.

GHSA-gvf2-2rh5-mpgf — OpenC3 COSMOS: Stored, cross-user XSS via Telemetry screen BUTTON widget

Affected: npm: @openc3/vue-common

## Summary A user who can save a telemetry **screen** (permission `system_set`) can embed JavaScript in a screen `BUTTON` widget. The `BUTTON` widget **`eval()`s the stored button text in the browser** when the button is activated, and screens are **shared content rendered to other users in the scope**. As a result, an attacker's stored JavaScript executes **in a different operator's authenticated session** — a **stored, cross-user XSS** (not self-XSS). The payload runs in the COSMOS origin and can read `localStorage.openc3Token` (the victim's session token), enabling **session/account takeover** and, via the victim's privileges, a path to server-side code execution through the Script Runner.

The site's Content-Security-Policy permits `'unsafe-inline'`/`'unsafe-eval'` (see "Contributing factor"), so the injected script runs unimpeded.

- **Product:** OpenC3 COSMOS (Core; likely Enterprise — see scoping note) - **Affected version:** confirmed **7.2.0** (latest, tested 2026-06-25); the code path is present on `main`. Lower bound for maintainer to confirm. - **Reporter:** _Arpit Kubadia_

## Description & root cause 1. **Screen save (the store):** `POST /openc3-api/screen` → `ScreensController#create` (`openc3-cosmos-cmd-tlm-api/app/controllers/screens_controller.rb:35-43`) persists the raw screen text after `authorization('system_set')`. No sanitization of the screen body. 2. **The sink (the execution):** the `BUTTON` widget stores the button's action as its second parameter…

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fkie_cve-2026-77394

GHSA-gvf2-2rh5-mpgf — OpenC3 COSMOS: Stored, cross-user XSS via Telemetry screen BUTTON widget