Unsafe inline XSS in pasting DOM element into chat

Impact

Inline scripts are executed when Javascript is parsed via a paste action.

1. Open https://watch.owncast.online/
2. Copy and then paste <img src=null onerror=alert('hello')> into the
   chat field.
3. An alert should pop up.

Patches

    ⋮ 13 │    // Content security policy
    ⋮ 14 │    csp := []string{
    ⋮ 15 │        "script-src 'self' 'sha256-2HPCfJIJHnY0NrRDPTOdC7AOSJIcQyNxzUuut3TsYRY='",
    ⋮ 16 │        "worker-src 'self' blob:", // No single quotes around blob:
    ⋮ 17 │    }

Will be patched in 0.0.9 by blocking unsafe-inline Content Security Policy and specifying the script-src. The worker-src is required to be set to blob for the video player.

For more information

If you have any questions or comments about this advisory:

• Open an issue in owncast/owncast
• Email us at gabek@real-ity.com