Reflected XSS Vulnerability in Discourse by Discourse
CVE-2017-20290

5.1MEDIUM

Key Information:

Vendor

Discourse
Status
Discourse
Vendor
CVE Published:
22 October 2026

What is CVE-2017-20290?

The software version of Discourse prior to 1.9.0.beta13 contains a vulnerability that allows unauthenticated attackers to execute scripts through a crafted GET request. Specifically, the email parameter of the /email/unsubscribed endpoint can be exploited via SVG onload payloads, leading to unescaped rendering of JavaScript in users' browsers. This vulnerability poses a significant risk as it can be exploited to hijack user sessions or execute malicious actions on behalf of the user without their consent.

Affected Version(s)

Discourse 1.9.0.beta2 < 1.9.0.beta13

References

https://github.com/discourse/discourse/commit/a6f2533d38
patch
https://github.com/discourse/discourse/commit/6e37f09b19
technical-descriptionpatch
https://github.com/projectdiscovery/nuclei-templates/blob...
technical-description

CVSS V4

Score:
5.1
Severity:
MEDIUM
Confidentiality:
None
Integrity:
None
Availability:
None
Attack Vector:
Network
Attack Complexity:
Low
Attack Required:
None
Privileges Required:
Undefined
User Interaction:
Unknown

Timeline

  • Vulnerability published

  • Vulnerability Reserved

Credit

The Shadowserver Foundation
.