CVE-2021-39183

HIGH8.2EPSS 0.33%

Unsafe inline XSS in pasting DOM element into chat

Published: 12/14/2021Modified: 3/13/2026

Description

### 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](https://github.com/owncast/owncast/issues) * Email us at [[email protected]](mailto:[email protected])

Affected packages (2)

CVSS scores

SourceVersionSeverityVector
osvCVSS 3.1HIGH8.2CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:H/A:L

References (3)