Discourse Activity Stream Cross-Site Scripting Vulnerability

A cross-site scripting (XSS) vulnerability has been identified in Discourse, an open-source community discussion platform. This issue affects versions prior to 3.3.3 in the stable branch and versions prior to 3.4.0.beta4 in the tests-passed branch. The vulnerability arises in activity streams on the user's profile page, but only under certain combinations of plugins and with Content Security Policy (CSP) disabled. In these scenarios, the activity streams may be exploited to inject malicious scripts.

Impact

Exploitation of this vulnerability allows for cross-site scripting, where an attacker can inject malicious scripts that are executed in the context of the user's browser.

Remediation

Users are advised to upgrade to Discourse version 3.3.3 or later in the stable branch, or version 3.4.0.beta4 or later in the tests-passed branch. For users unable to upgrade, it is recommended to enable Content Security Policy.