What’s Vulnerable › Vulnerabilities

CVE-2026-72720: Discourse: HTML injection in PrettyText.format_for_email from cooked-attribute reparsing

• Severity: medium (CVSS 6.4 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-08-10 · updated 2026-09-08
• Weakness: CWE-79

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.

Affected products

• discourse: before 2026.1.7; from 2026.6.0-latest, < 2026.6.2; from 2026.7.0-latest, < 2026.7.1; from 2026.8.0-latest, < 2026.8.0-latest.1

References

• 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
• 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/security/advisories/GHSA-3q6f-6gm9-m35v

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