# CVE-2026-55674: Discourse: Cache poisoning/XSS via color scheme cookies

> Unauthenticated attackers can inject arbitrary JavaScript via crafted cookies, bypassing CSP to execute code in visitors' browsers.

- **Severity:** Critical 9.3 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 17 Aug 2026
- **Updated:** 18 Aug 2026
- **Also known as:** BIT-discourse-2026-55674, GHSA-qx4v-rg4v-pm2g

## What is CVE-2026-55674?

CVE-2026-55674 is a critical cross-site scripting vulnerability in discourse, published on 17 Aug 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

Discourse is an open-source discussion platform. Prior to 2026.1.6, 2026.5.2, 2026.6.1, and 2026.7.0, an unauthenticated attacker could send a single request with a crafted color_scheme_id (or dark_scheme_id) cookie to inject arbitrary HTML into a Discourse page. Because the cookie value was rendered into a color scheme tag without escaping, the attacker could break out of the attribute and inject a tag that bypassed Discourse's nonce-based Content Security Policy, resulting in arbitrary JavaScript execution in visitors' browsers. This issue is fixed in versions 2026.1.6, 2026.5.2, 2026.6.1, and 2026.7.0.

Weakness: CWE-79 (Improper Neutralization of Input During Web Page Generation)

## Which versions are affected by CVE-2026-55674?

1 open source package ship an affected version, including discourse.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `discourse` | Bitnami | All versions | 2026.1.6, 2026.5.2, 2026.6.1 |

## How do I fix CVE-2026-55674?

Upgrade discourse to a fixed version for your release line: 2026.1.6, 2026.5.2 or 2026.6.1.

## Is CVE-2026-55674 being exploited?

There is no known exploitation of CVE-2026-55674 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-55674 and fix it if it is affected.

What it is: CVE-2026-55674 is a critical cross-site scripting vulnerability in discourse, published on 17 Aug 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2026-55674 in the wild and no public exploit code.

Affected packages and fixed versions:
- discourse (Bitnami): affected all versions; fixed in 2026.1.6, 2026.5.2, 2026.6.1

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-55674/ (Markdown: https://insights.sbomify.com/CVE-2026-55674/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-55674
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-55674
- OSV: https://osv.dev/vulnerability/CVE-2026-55674

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-55674/
Summaries are generated and may contain mistakes; the official description above is the record.