Discourse is an open-source discussion platform. From versions 2026.1.0-latest to before 2026.1.3, 2026.2.0-latest to before 2026.2.2, and 2026.3.0-latest to before 2026.3.0, an attacker with the ability to create shared AI conversations could inject arbitrary HTML and JavaScript via crafted conversation titles. This payload would execute in the browser of any user viewing the onebox preview, potentially allowing session hijacking or unauthorized actions on behalf of the victim.
This issue has been patched in versions 2026.1.3, 2026.2.2, and 2026.3.0.
Attack Parameters
Attack Vector
Network
Can be exploited remotely
Attack Complexity
Low
Easy to exploit
Attack Requirements
None
No additional conditions
Privileges Required
Low
Basic privileges needed
User Interaction
None
No user interaction needed
Impact Assessment
Confidentiality
None
No data leak
Integrity
Low
Partial data modification
Availability
None
No disruption
CVSS Vector v4.0
Weakness Type (CWE)
Vulnerable Products 4
| Configuration | From (including) | Up to (excluding) |
|---|---|---|
|
Discourse Discourse
cpe:2.3:a:discourse:discourse:*:*:*:*:latest:*:*:*
|
2026.1.0
|
2026.1.3
|
|
Discourse Discourse
cpe:2.3:a:discourse:discourse:*:*:*:*:latest:*:*:*
|
2026.2.0
|
2026.2.2
|
|
Discourse Discourse
cpe:2.3:a:discourse:discourse:2026.3.0:*:*:*:latest:*:*:*
|
— | — |
|
Discourse Discourse
cpe:2.3:a:discourse:discourse:2026.3.0:*:*:*:latest.1:*:*:*
|
— | — |