CVE intelligence and bounded remediation

CVE-2021-41095 — Discourse is an open source discussion platform

Medium CVSS 6.1

Discourse is an open source discussion platform. There is a cross-site scripting (XSS) vulnerability in versions 2.7.7 and earlier of the `stable` branch, versions 2.8.0.beta6 and earlier of the `beta` branch, and versions 2.8.0.beta6 and earlier of the `tests-passed` branch. Rendering of some error messages that contain user input can be susceptible to XSS attacks. This vulnerability only affects sites which have blocked watched words that contain HTML tags, modified or disabled Discourse's default Content Security Policy. This issue is patched in the latest `stable`, `beta` and `tests-passed` versions of Discourse. As a workaround, avoid modifying or disabling Discourse’s default Content Security Policy, and blocking watched words containing HTML tags.

Severity
Medium
CVSS
6.1 (3.1)
Published
2021-09-27
CISA KEV
Not currently listed
Ecosystem
software/application
Weaknesses
CWE-79

Affected products

  • discourse / discourse
  • discourse / discourse / 2.8.0

Showing 2 representative product identities from 7 source matches. Confirm exact affected versions with the linked vendor and NVD evidence.

Matched remediation archetype

Cross-site scripting and unsafe browser output

This catalog composition supplies bounded fallback guidance. Explicitly reviewed curated workflows load with the complete record below.

Check exposure

  • Trace reflected, stored, and DOM-derived untrusted values into HTML, attributes, URLs, styles, scripts, and client-side template sinks.
  • Identify affected origins, authenticated user roles, sensitive browser capabilities, and where content is shared across tenants.
  • Review framework escaping, rich-text sanitization, legacy templates, and client-side rendering paths.

Remediate safely

  • Use context-aware framework output encoding and safe DOM APIs; keep untrusted data out of executable contexts.
  • Sanitize intentionally supported markup with a maintained allowlist policy and validate URLs and attributes separately.
  • Update affected rendering components and add tests for every output context using inert sentinel markup.

Authoritative sources

Complete CVE record and remediation plan

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