CVE-2026-13323: eclipse foundation eclipse open vsx Cross-site Scripting

Vulnerability summary

CVE-2026-13323 is a high (CVSS 8.7) Cross-site Scripting vulnerability in eclipse foundation eclipse open vsx. EPSS estimates a 0.33% chance of exploitation in the next 30 days, higher than 24.7% of scored vulnerabilities. 1 public exploit is recorded.

Timeline

1. 01-07-2026
   PublishedVulnerability first disclosed.
2. 01-07-2026
   Last modifiedVulnerability information updated.

Description

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.

• CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.