# CVE-2026-32308: OneUptime: Stored XSS via Mermaid Diagram Rendering (securityLevel: "loose")

> Attackers can execute arbitrary JavaScript via stored XSS in Mermaid diagrams rendered in markdown fields, potentially compromising user accounts.

- **Severity:** High 7.6 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:L/A:N`)
- **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:** Yes
- **Published:** 12 Mar 2026
- **Updated:** 14 Mar 2026
- **Also known as:** GHSA-wvh5-6vjm-23qh

## What is CVE-2026-32308?

CVE-2026-32308 is a high-severity cross-site scripting vulnerability in oneuptime, published on 12 Mar 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.

### Official description

OneUptime is a solution for monitoring and managing online services. Prior to 10.0.23, the Markdown viewer component renders Mermaid diagrams with securityLevel: "loose" and injects the SVG output via innerHTML. This configuration explicitly allows interactive event bindings in Mermaid diagrams, enabling XSS through Mermaid's click directive which can execute arbitrary JavaScript. Any field that renders markdown (incident descriptions, status page announcements, monitor notes) is vulnerable. This vulnerability is fixed in 10.0.23.

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

## Which versions are affected by CVE-2026-32308?

2 open source packages ship an affected version, including oneuptime. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `oneuptime` | npm | All versions | 10.0.23 |
| `oneuptime` | npm | All versions | 10.0.23 |

Products: Hackerbay Oneuptime.

## How do I fix CVE-2026-32308?

Upgrade oneuptime to 10.0.23 or later.

## Is CVE-2026-32308 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-32308 exists.

## Other vulnerabilities in oneuptime

- [CVE-2026-33396](https://insights.sbomify.com/CVE-2026-33396/): Code injection in oneuptime (critical 10.0)
- [CVE-2026-32306](https://insights.sbomify.com/CVE-2026-32306/): OneUptime ClickHouse SQL Injection via Aggregate Query Parameters (critical 10.0)
- [CVE-2026-30956](https://insights.sbomify.com/CVE-2026-30956/): OneUptime has authorization bypass via client‑controlled is-multi-tenant-query header (critical 10.0)
- [CVE-2026-30957](https://insights.sbomify.com/CVE-2026-30957/): OneUptime Synthetic Monitor RCE via exposed Playwright browser object (critical 10.0)
- [CVE-2026-30887](https://insights.sbomify.com/CVE-2026-30887/): OneUptime Affected by Unsandboxed Code Execution in Probe Allows Any Project Member to Achieve RCE (critical 10.0)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-32308 and fix it if it is affected.

What it is: CVE-2026-32308 is a high-severity cross-site scripting vulnerability in oneuptime, published on 12 Mar 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-32308 exists.

Affected packages and fixed versions:
- oneuptime (npm): affected all versions; fixed in 10.0.23
- oneuptime (npm): affected all versions; fixed in 10.0.23

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-2026-32308/ (Markdown: https://insights.sbomify.com/CVE-2026-32308/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-32308
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-32308
- OSV: https://osv.dev/vulnerability/CVE-2026-32308

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-32308/
Summaries are generated and may contain mistakes; the official description above is the record.