XSS in Discourse
CVE-2017-20290
Discourse 1.9.0.beta2 before 1.9.0.beta13 contains a reflected cross-site scripting vulnerability that allows unauthenticated attackers to inject scripts through the email parameter of /email/unsubscribed. Attackers can craft GET requests with SVG onload payloads, which unsubscribed.html.erb renders unescaped via html_safe, executing JavaScript in victims' browsers. Exploitation evidence was first observed by the Shadowserver Foundation on 2023-10-19.
Vulnerability class: XSS (Cross-Site Scripting)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 6.1 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N.
EPSS exploit prediction
No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.
Affected products
Weakness classification (CWE)
References
- github.com/discourse/discourse/commit/a6f2533d38 (patch)
- github.com/discourse/discourse/commit/6e37f09b19 (technical-description, patch)
- github.com/projectdiscovery/nuclei-templates/blob/main/http/vulnerabilities/oth… (technical-description)
- www.vulncheck.com/advisories/discourse-1.9.0-beta13-reflected-xss-via-email-uns… (third-party-advisory)
Frequently asked questions
- What is CVE-2017-20290?
- CVE-2017-20290 is a medium-severity vulnerability in Discourse, classified under Cross-site Scripting. CVSS score: 6.1/10. Published 2026-10-22.
- How severe is CVE-2017-20290?
- Medium severity. CVSS v3 base score is 6.1 out of 10.