Discourse: HTML injection in PrettyText.format_for_email from cooked-attribute reparsing
Key facts
- Attack vector
- Network
- Privileges required
- Low
- User interaction
- None
- Attack complexity
- Low
- Impact type
- Cross-site scripting
- Confidentiality · integrity · availability
- Low · Low · None
- Fix status
- Fixed
Attack profile from CVSS 3.1 · CNA. Fix status from CNA. Impact type from CWE-79.
Summary
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.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- No
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| discourse | discourse | before 2026.1.7; 2026.6.0-latest to before 2026.6.2; 2026.7.0-latest to before 2026.7.1; 2026.8.0-latest to before 2026.8.0-latest.1 | 2026.1.7, 2026.6.2, 2026.7.1, 2026.8.0-latest.1 | Patch available | CNA |
- discourse Vendordiscourse Affected before 2026.1.7; 2026.6.0-latest to before 2026.6.2; 2026.7.0-latest to before 2026.7.1; 2026.8.0-latest to before 2026.8.0-latest.1 Fixed in 2026.1.7, 2026.6.2, 2026.7.1, 2026.8.0-latest.1 Patch available CNA
Remediation
- Fix · CNA discourse (discourse) Fixed in 2026.1.7, 2026.6.2, 2026.7.1, 2026.8.0-latest.1
Timeline
- 2026-10-02 Threatist record created from CVE-2026-72720
References
Other 9
- 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
More discourse vulnerabilities
- TI-2022-22806 Discourse BBCode plugin vulnerable to arbitrary CSS injection CVSS 3.1CRITICAL 9.8
- TI-2021-19656 Denial of Service in discourse CVSS 3.1MEDIUM 6.8
- TI-2024-36150 Potential Backup file leaked via Nginx in Discourse CVSS 3.1HIGH 7.5
- TI-2021-18002 RCE via malicious SNS subscription payload CVSS 3.1CRITICAL 10.0
- TI-2026-24651 Discourse: Open redirect via `sso_destination_url` cookie in `enter` CVSS 4.0MEDIUM 5.1
- TI-2022-18730 Discourse Patreon vulnerable to improper validation of email during Patreon authentication CVSS 3.1CRITICAL 9.8
Sources
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences