# CVE-2026-1009: Stored Cross-Site Scripting in Altium Live Forum Leading to Cross-Customer Data Exposure

> An authenticated attacker can inject JavaScript into forum posts to steal workspace data and hijack sessions of other users viewing the post.

- **Severity:** Critical 9.0 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:H`)
- **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:** 15 Jan 2026
- **Updated:** 20 Jan 2026
- **Also known as:** GHSA-fc5v-qvgj-pv25

## What is CVE-2026-1009?

CVE-2026-1009 is a critical cross-site scripting vulnerability in Altium Live, published on 15 Jan 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

A stored cross-site scripting (XSS) vulnerability exists in the Altium Forum due to missing server-side input sanitization in forum post content. An authenticated attacker can inject arbitrary JavaScript into forum posts, which is stored and executed when other users view the affected post.
Successful exploitation allows the attacker’s payload to execute in the context of the victim’s authenticated Altium 365 session, enabling unauthorized access to workspace data, including design files and workspace settings. Exploitation requires user interaction to view a malicious forum post.

Weakness: CWE-79 (Improper Neutralization of Input During Web Page Generation), CWE-284 (Improper Access Control)

## Which versions are affected by CVE-2026-1009?

It affects 1 product.


Products: Altium Altium Live.

## How do I fix CVE-2026-1009?

No fix has been published for CVE-2026-1009 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-1009 being exploited?

There is no known exploitation of CVE-2026-1009 in the wild and no public exploit code.

## Other vulnerabilities in Altium Live

- [CVE-2026-1008](https://insights.sbomify.com/CVE-2026-1008/): Stored Cross-Site Scripting in Altium Live User Profile Fields (high 7.6)
- [CVE-2026-1011](https://insights.sbomify.com/CVE-2026-1011/): Stored Cross-Site Scripting in Altium Live Support Center Comment Endpoint (medium 6.1)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-1009 and fix it if it is affected.

What it is: CVE-2026-1009 is a critical cross-site scripting vulnerability in Altium Live, published on 15 Jan 2026. 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-2026-1009 in the wild and no public exploit code.

Affected product: Altium Live. 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-2026-1009/ (Markdown: https://insights.sbomify.com/CVE-2026-1009/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-1009
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-1009
- OSV: https://osv.dev/vulnerability/CVE-2026-1009

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-1009/
Summaries are generated and may contain mistakes; the official description above is the record.