Risk Letters

Exploited vulnerability

CVE-2017-20290

TLP:CLEAR

discourse discourse Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

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.

Facts

  • Vendor: Discourse
  • Product: Discourse
  • EPSS (probability of exploitation within 30 days): 0.3 %
  • First known exploitation: 22 October 2026
  • First seen by Risk Letters: 22 October 2026

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Data: NVD (public domain), CISA KEV, FIRST EPSS, MITRE ATT&CK, AlienVault OTX. NVD