CVE-2026-27570 PUBLISHED

Discourse Vulnerable to Stored XSS via Shared AI Conversation Onebox

Assigner: GitHub_M
Reserved: 20.02.2026 Published: 19.03.2026 Updated: 19.03.2026

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.

Metrics

CVSS 4.0

CVSS 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
CVSS Score: 5.1

Exploitability Metrics		Vulnerable System Impact Metrics		Subsequent System Impact Metrics
Attack Vector	Network	Confidentiality	Low	Confidentiality	None
Attack Complexity	Low	Integrity	Low	Integrity	None
Attack Requirements	None	Availability	None	Availability	None
Privileges Required	Low
User Interaction	Passive

CVSS 4.0

Product Status

Vendor	discourse
Product	discourse
Versions	Version >= 2026.1.0-latest, < 2026.1.2 is affected Version >= 2026.2.0-latest, < 2026.2.1 is affected Version = 2026.3.0-latest is affected

References

Problem Types

CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') CWE