# CVE-2026-4983: Cross-site scripting in Eclipse Open VSX

> Attackers can achieve stored XSS via malicious SVG icons, leading to session hijacking and token theft on local deployments.

- **Severity:** Medium 4.1 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:N/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:** No
- **Published:** 23 Jun 2026
- **Updated:** 23 Jun 2026
- **Also known as:** GHSA-xpqg-5hj3-ggmh

## What is CVE-2026-4983?

CVE-2026-4983 is a medium-severity cross-site scripting vulnerability in Eclipse Open VSX, published on 23 Jun 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

Open VSX Registry does not sanitize SVG files uploaded as extension icons prior to storage, and serves them with Content-Type: image/svg+xml without security headers such as Content-Security-Policy or Content-Disposition: attachment. This allows an attacker to publish an extension with a malicious SVG icon and achieve stored cross-site scripting (XSS) when a user navigates directly to the icon URL.

On deployments using local storage, script execution occurs within the Open VSX application origin, enabling session hijacking, authentication token theft, and unauthorized extension publishing. On deployments backed by external storage (such as open-vsx.org with an S3-backed CDN), execution is confined to the storage origin, reducing impact but still permitting phishing attacks and credential harvesting through attacker-crafted pages.

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

## Which versions are affected by CVE-2026-4983?

It affects 1 product.


Products: Eclipse Open Vsx.

## How do I fix CVE-2026-4983?

No fix has been published for CVE-2026-4983 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-4983 being exploited?

There is no known exploitation of CVE-2026-4983 in the wild and no public exploit code.

## Other vulnerabilities in Eclipse Open VSX

- [CVE-2025-6705](https://insights.sbomify.com/CVE-2025-6705/): Privilege escalation in Eclipse Open VSX Registry (high 7.6)
- [CVE-2025-1007](https://insights.sbomify.com/CVE-2025-1007/): Improper Authorization in /user/namespace/{namespace}/details (medium 6.9)
- [CVE-2026-13323](https://insights.sbomify.com/CVE-2026-13323/): Cross-site scripting in Eclipse Open VSX (medium 4.1)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-4983 and fix it if it is affected.

What it is: CVE-2026-4983 is a medium-severity cross-site scripting vulnerability in Eclipse Open VSX, published on 23 Jun 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-2026-4983 in the wild and no public exploit code.

Affected product: Eclipse Open VSX. 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-2026-4983/ (Markdown: https://insights.sbomify.com/CVE-2026-4983/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-4983
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-4983
- OSV: https://osv.dev/vulnerability/CVE-2026-4983

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-4983/
Summaries are generated and may contain mistakes; the official description above is the record.