Discourse User Full Name HTML Evaluation Leading to Cross-Site Scripting Vulnerability

A cross-site scripting (XSS) vulnerability has been identified in Discourse, an open-source discussion platform. This issue affects versions prior to 2025.12.2, 2026.1.1, and 2026.2.0. The vulnerability arises when the settings 'display_name_on_posts' is enabled and 'prioritize_username_in_ux' is disabled, allowing a user's full name to be processed as raw HTML. Consequently, editing a post from a malicious user could trigger an XSS attack.

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 versions 2025.12.2, 2026.1.1, or 2026.2.0, which address this vulnerability.