CVE-2026-27570CWE-79

Discourse Vulnerable to Stored XSS via Shared AI Conversation Onebox

Medium · published March 19, 2026

CVSS v4.0
5.1
EPSS
0%
Percentile
28.3
In the wild
Unconfirmed
What it is

Discourse is an open-source discussion platform. Prior to versions 2026.3.0-latest.1, 2026.2.1, and 2026.1.2, the onebox method in the SharedAiConversation model renders the conversation title directly into HTML without proper sanitization. Versions 2026.3.0-latest.1, 2026.2.1, and 2026.1.2 contain a patch. As a workaround, tighten access by changing the `ai_bot_public_sharing_allowed_groups` site setting.

The record
Technical detail
CVSS v4.0
5.1 · MEDIUM
Vector
CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:P/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N
EPSS
0.00358 · 28.3th percentile
Weakness
CWE-79 · Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Published
2026-03-19T20:52Z
EPSS history
Timeline
  • 19 MAR 20:52Z
    Discourse Vulnerable to Stored XSS via Shared AI Conversation Onebox
    cvelistv5