# CVE-2023-33186: Cross-site scripting vulnerability in Zulip Server development branch via topic tooltip

> An attacker can execute arbitrary JavaScript in a victim's browser by crafting a malicious message topic that triggers XSS via tooltip hover.

- **Severity:** High 8.2 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:L/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 30 May 2023
- **Updated:** 10 Jan 2025
- **Also known as:** GHSA-4r83-8f94-hrph

## What is CVE-2023-33186?

CVE-2023-33186 is a high-severity cross-site scripting vulnerability in zulip, published on 30 May 2023. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.

### Official description

Zulip is an open-source team collaboration tool with unique topic-based threading that combines the best of email and chat to make remote work productive and delightful. The main development branch of Zulip Server from May 2, 2023 and later, including beta versions 7.0-beta1 and 7.0-beta2, is vulnerable to a cross-site scripting vulnerability in tooltips on the message feed. An attacker who can send messages could maliciously craft a topic for the message, such that a victim who hovers the tooltip for that topic in their message feed triggers execution of JavaScript code controlled by the attacker.

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

## Which versions are affected by CVE-2023-33186?

It affects 1 product.


Products: Zulip Zulip Server.

## How do I fix CVE-2023-33186?

No fix has been published for CVE-2023-33186 yet. Limit exposure of the affected software until one is available.

## Is CVE-2023-33186 being exploited?

There is no known exploitation of CVE-2023-33186 in the wild and no public exploit code.

## Other vulnerabilities in zulip

- [CVE-2019-18933](https://insights.sbomify.com/CVE-2019-18933/): Information disclosure in n/a (critical 9.8)
- [CVE-2020-15070](https://insights.sbomify.com/CVE-2020-15070/): Code injection in n/a (high 8.8)
- [CVE-2017-0910](https://insights.sbomify.com/CVE-2017-0910/): Missing authorization in Zulip Server (high 8.8)
- [CVE-2025-31478](https://insights.sbomify.com/CVE-2025-31478/): Zulip Authentication Backend Configuration Bypass (high 8.2)
- [CVE-2024-36612](https://insights.sbomify.com/CVE-2024-36612/): Denial of service in n/a (high 7.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2023-33186 and fix it if it is affected.

What it is: CVE-2023-33186 is a high-severity cross-site scripting vulnerability in zulip, published on 30 May 2023. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2023-33186 in the wild and no public exploit code.

Affected product: zulip. 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-2023-33186/ (Markdown: https://insights.sbomify.com/CVE-2023-33186/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-33186
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-33186
- OSV: https://osv.dev/vulnerability/CVE-2023-33186

---
From sbomify Insights: https://insights.sbomify.com/CVE-2023-33186/
Summaries are generated and may contain mistakes; the official description above is the record.