# CVE-2026-35208: lichess.org has an Unsanitized Stream Title Injection on /streamer

> Approved streamers can inject arbitrary HTML into the streamer page and homepage widget via unsanitized stream titles, bypassing CSP restrictions.

- **Severity:** Medium 5.3 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 6 Apr 2026
- **Updated:** 7 Apr 2026
- **Also known as:** GHSA-v7gh-939r-pfjq

## What is CVE-2026-35208?

CVE-2026-35208 is a medium-severity cross-site scripting vulnerability in lichess-org lila, published on 6 Apr 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

lichess.org is the forever free, adless and open source chess server. Any approved streamer can inject arbitrary HTML into /streamer and the homepage “Live streams” widget by placing markup in their Twitch/YouTube stream title. CSP is present and blocks inline script execution, but the issue is still a server-side HTML injection sink. To trigger this, a Lichess account only needs to satisfy the normal streamer requirements and get approved. Per Streamer.canApply, that means an account older than 2 days with at least 15 games, or a verified/titled account. After moderator approval, once the streamer goes live, Lichess pulls the platform title and renders it into the UI as-is. No extra privileges are needed beyond a normal approved streamer profile. This vulnerability is fixed with commit 0d5002696ae705e1888bf77de107c73de57bb1b3.

Weakness: CWE-79 (Improper Neutralization of Input During Web Page Generation), CWE-116 (Improper Encoding or Escaping of Output)

## Which versions are affected by CVE-2026-35208?

It affects 1 product.


Products: Lichess Lila.

## How do I fix CVE-2026-35208?

No fix has been published for CVE-2026-35208 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-35208 being exploited?

There is no known exploitation of CVE-2026-35208 in the wild and no public exploit code.

## Other vulnerabilities in lichess-org lila

- [CVE-2025-52186](https://insights.sbomify.com/CVE-2025-52186/): Server-side request forgery in n/a (medium 6.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-35208 and fix it if it is affected.

What it is: CVE-2026-35208 is a medium-severity cross-site scripting vulnerability in lichess-org lila, published on 6 Apr 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-35208 in the wild and no public exploit code.

Affected product: lichess-org lila. No package-level version data is available, so check the vendor advisory linked from the reference page.

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-2026-35208/ (Markdown: https://insights.sbomify.com/CVE-2026-35208/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-35208
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-35208
- OSV: https://osv.dev/vulnerability/CVE-2026-35208

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-35208/
Summaries are generated and may contain mistakes; the official description above is the record.