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.
- 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
- None listed
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
Which versions are affected by CVE-2026-4983?
It affects 1 product.
Products include 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.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
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
Sources
Also known as GHSA-xpqg-5hj3-ggmh.