Critical Vulnerabilities in Popular VS Code Extensions Enable Local File Theft and Code Execution

Security researchers at OX Security disclosed multiple vulnerabilities across widely used Microsoft Visual Studio Code extensions—Live Server, Code Runner, Markdown Preview Enhanced, and Microsoft Live Preview—with combined installs reported at 125–128 million. The issues enable attacks ranging from local file exfiltration to arbitrary code/JavaScript execution, and highlight how a single vulnerable or malicious extension can be leveraged for broader compromise and potential lateral movement in developer environments.

Reported flaws include CVE-2025-65717 (Live Server; CVSS 9.1) enabling local file theft by luring a developer to a malicious site while the extension’s local server is running (e.g., localhost:5500), CVE-2025-65716 (Markdown Preview Enhanced; CVSS 8.8) allowing arbitrary JavaScript execution via a crafted .md file with subsequent local port enumeration and exfiltration, and CVE-2025-65715 (Code Runner; CVSS 7.8) enabling code execution by tricking users into modifying settings.json. Separate reporting on Microsoft Live Preview describes a one-click reflected XSS and unauthenticated request abuse against the extension’s local development server to enumerate and exfiltrate sensitive files (e.g., .env, API keys, source code); this Live Preview issue was reported as patched in version 0.4.16 via input sanitization (e.g., an escapeHTML function), while other extension issues were described as unpatched at the time of reporting.