Full Report
Cybersecurity researchers have disclosed multiple security vulnerabilities in four popular Microsoft Visual Studio Code (VS Code) extensions that, if successfully exploited, could allow threat actors to steal local files and execute code remotely. The extensions, which have been collectively installed more than 125 million times, are Live Server, Code Runner, Markdown Preview Enhanced, and
Analysis Summary
# Vulnerability: Multiple Critical Flaws in VS Code Extensions
## CVE Details
* **CVE-2025-65717**: CVSS 9.1 (Critical) - Live Server exfiltration
* **CVE-2025-65716**: CVSS 8.8 (High) - Markdown Preview Enhanced RCE/Exfiltration
* **CVE-2025-65715**: CVSS 7.8 (High) - Code Runner RCE
* **No CVE assigned**: Microsoft Live Preview (Fixed)
## Affected Systems
- **Products**: Microsoft Visual Studio Code (VS Code) Extensions
- **Affected Extensions**:
- **Live Server** (All versions up to current)
- **Markdown Preview Enhanced** (All versions up to current)
- **Code Runner** (All versions up to current)
- **Microsoft Live Preview** (Versions prior to 0.4.16)
- **Configurations**: Extensions must be active; specifically when developers run local HTTP development servers (localhost).
## Vulnerability Description
Security researchers from OX Security identified flaws revolving around Cross-Site Scripting (XSS) and insecure handling of local servers:
* **Arbitrary File Access/Exfiltration**: Attackers can use malicious websites or crafted files to interact with the local HTTP servers established by extensions (like Live Server). This allows the extraction of local files via JavaScript when a developer visits a malicious link while the extension is running.
* **Remote Code Execution (RCE)**: Flaws in Code Runner allow attackers to execute arbitrary code by manipulating the `settings.json` file through social engineering. In Markdown Preview, malicious `.md` files can execute JavaScript to perform port enumeration and data exfiltration.
## Exploitation
- **Status**: PoC available (disclosed by OX Security); no confirmed "in-the-wild" exploitation reported yet.
- **Complexity**: Medium (Requires enticing a developer to visit a link, download a repository, or open a crafted file).
- **Attack Vector**: Network/Remote (via malicious web pages or crafted files).
## Impact
- **Confidentiality**: High (Source code, environment variables, and local files can be stolen).
- **Integrity**: High (Ability to execute code or modify configurations).
- **Availability**: Medium (Potential local system compromise).
## Remediation
### Patches
- **Microsoft Live Preview**: Update to **version 0.4.16 or later**.
- **Live Server / Code Runner / Markdown Preview**: No patches available as of the reporting date (Unpatched).
### Workarounds
- **Disable/Uninstall**: Remove the affected extensions if they are not mission-critical.
- **Configuration Hygiene**: Do not apply untrusted `settings.json` configurations or open Markdown files from unknown sources.
- **Active Management**: Turn off localhost-based services and extensions when they are not actively being used for development.
## Detection
- **Indicators of Compromise**:
- Unexpected outbound traffic from the IDE or local development ports (e.g., localhost:5500) to unknown external domains.
- Modified `settings.json` files containing unexpected script execution paths.
- **Detection Methods**:
- Monitor network logs for local port enumeration behaviors.
- Use host-based security tools to monitor for unauthorized file access by the VS Code process.
## References
- **OX Security Research**: hxxps[://]www[.]ox[.]security/blog/four-vulnerabilities-expose-a-massive-security-blind-spot-in-ide-extensions/
- **Live Preview Changelog**: hxxps[://]github[.]com/microsoft/vscode-livepreview/blob/main/CHANGELOG[.]md
- **THN Article**: hxxps[://]thehackernews[.]com/2026/02/critical-flaws-found-in-four-vs-code[.]html