Discourse XSS and Information Disclosure Flaws

Discourse versions prior to 3.5.0.beta6 contain a reflected cross-site scripting (XSS) vulnerability in social login functionality that is only exploitable when Content Security Policy (CSP) is disabled. An unauthenticated attacker can craft a malicious link leveraging social authentication endpoints to inject arbitrary JavaScript, potentially stealing session tokens, credentials, or performing actions on behalf of the victim. The vulnerability requires user interaction (clicking a malicious link) but has high impact on confidentiality and integrity with no availability impact.

Discourse versions prior to 3.4.6 (stable) and 3.5.0.beta8-dev (tests-passed) contain an information disclosure vulnerability where users retain visibility of their own whisper-typed posts even after losing group membership that should restrict access to whispers. This is a logic flaw in the whisper visibility enforcement mechanism (CWE-200: Information Exposure) affecting unauthenticated network access with high confidentiality impact. No public exploitation has been reported, but the issue is easily discoverable through normal platform usage.