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.
- No active-exploitation, high-EPSS, or public-exploit signals - routine patching cadence
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:N/I:L/A:NATT&CK techniques
2Techniques this CVE enables. Pills with a solid outline are high confidence - named directly in ATT&CK or Nuclei, or human-curated by CTID; the rest are inferred from the weakness type using MITRE's CVE Mapping Methodology and the CWE → CAPEC chain. Broad, generic-weakness guesses are filtered out. A small N× marks a technique that N independent sources agree on.
▤ Build a SIEM detection for these techniquesCAPEC attack patterns
6Attack patterns this CVE enables - the bridge from weakness to ATT&CK technique.