CVE-2026-91120

5.4 MEDIUM 0.2% exploit odds Fix listed XSS Browser & mail

What it is

Discourse is an open-source discussion platform. Prior to 2026.1.8, 2026.6.3, 2026.7.2, and 2026.8.0, provider-controlled video titles in lazy video embeds could be reparsed as HTML when Discourse generated notification emails or chat summaries. A user with standard posting privileges could create a post for an enabled YouTube, Vimeo, or TikTok provider whose title contained markup, and the email and chat-summary rendering path would place that markup into the output instead of treating it solely as text. Recipients using HTML-capable email clients could see injected content, potentially including event handlers, but the issue did not directly expose a Discourse browser session or affect the forum page itself. Lazy video embeds must be enabled, which is the default configuration. This issue is fixed in versions 2026.1.8, 2026.6.3, 2026.7.2, and 2026.8.0.

At a glance

Exploitability: Can be exploited over the network with a low-privilege account. Limited direct impact.
Exploit odds: 0.2% chance of exploitation in the next 30 days (EPSS).
Fix: A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

2026-09-24 18:19 UTC PublishedDisclosed publicly on CVE.org and NVD
2026-09-24 18:19 UTC Last updatedMost recent change to the record

Why it ranks here

Exploited in the wild: no, CISA does not list it.
Exploit odds: 0.2% in the next 30 days (EPSS).
Severity: 5.4 MEDIUM (CVSS).
Fix: a patch or advisory is linked.

Details

Published: 2026-09-24 18:19 UTC
Last modified: 2026-09-24 18:19 UTC
Exploit probability: 0.2% · EPSS, next 30 days
Weakness: CWE-79 · Cross-site scripting
Record status: Deferred

Attack profile CVSS 3.1 · 5.4

Attack vector: Network
Complexity: Low
Privileges needed: Low
User interaction: None
Scope: Unchanged
Confidentiality: Low
Integrity: Low
Availability: None

Raw vector

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2026-91120.md and follow it. Check whether this project is affected by CVE-2026-91120. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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Fix and advisories

References

NVD record · CVE.org record