XSS in Eclipse Open Vsx
CVE-2026-13323
In Open VSX Registry before 1.0.2, the /vscode/unpkg/ endpoint serves user-supplied HTML files with Content-Type: text/html and without a Content-Security-Policy or Content-Disposition: attachment response header. An unauthenticated attacker can register a publisher account, upload a VSIX containing a crafted HTML payload, and induce an authenticated user to visit the resulting URL. The browser renders the file inline in the open-vsx.org origin context, enabling session token exfiltration, persistent Personal Access Token (PAT) generation, and unauthorized publication of malicious extension versions. Because Open VSX extensions are distributed to VS Code, VSCodium, Cursor, Windsurf, and compatible editors, a compromised extension update constitutes a supply chain attack against all downstream users.
Vulnerability class: XSS (Cross-Site Scripting)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 4.1 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:N/I:L/A:N.
EPSS exploit prediction
EPSS: 0.003 (23.9th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 24th percentile — 23.9% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.003 · newest: 0.003 · change: 0.000
Affected products
- Eclipse Open Vsx
- Eclipse Foundation Open Vsx — versions 0.1.0
Weakness classification (CWE)
References
- gitlab.eclipse.org/security/vulnerability-reports/-/work_items/485 (Exploit, Issue Tracking, Vendor Advisory)
- github.com/eclipse-openvsx/openvsx/pull/1922 (Patch, Issue Tracking)
Frequently asked questions
- What is CVE-2026-13323?
- CVE-2026-13323 is a medium-severity vulnerability in Eclipse Open Vsx, classified under Cross-site Scripting. CVSS score: 4.1/10. Published 2026-07-01.
- How severe is CVE-2026-13323?
- Medium severity. CVSS v3 base score is 4.1 out of 10.