Critical VS Code Extension Vulnerabilities Expose Developers to File Theft and Remote Code Execution.

Several high-profile extensions in Microsoft Visual Studio Code (VS Code) — with over 125 million combined installs — have been found to contain critical vulnerabilities that could allow attackers to steal local files or execute malicious code.

Affected extensions include:

• Live Server

• Code Runner

• Markdown Preview Enhanced

• Microsoft Live Preview (patched silently in version 0.4.16)

Let’s break it down.

What Is It?

Security researchers identified multiple vulnerabilities (including CVSS scores as high as 9.1) that allow attackers to:

• Exfiltrate sensitive local files

• Execute arbitrary code

• Enumerate local ports

• Move laterally across systems

In several cases, exploitation requires nothing more than:

• Visiting a malicious website while the extension is running

• Opening a crafted markdown file

• Being tricked into modifying a settings file

Three of the four vulnerabilities remain unpatched, meaning developers and organizations may currently be exposed.

This is a powerful reminder: one vulnerable extension is enough to compromise an entire development environment.

Why Should You Care?

If your organization uses VS Code — especially in development, DevOps, or IT teams — this is not just a developer issue. It’s a business risk.

Here’s why:

• 🔓 Localhost services can expose sensitive project files

• 📂 Source code, credentials, API keys, and tokens may be accessible

• 🖥️ Remote code execution can lead to full machine compromise

• 🏢 One infected developer device can lead to lateral movement across the organization

Development environments often have elevated permissions and access to production infrastructure. That makes them a high-value target.

This isn’t about “bad coding.” It’s about supply chain risk inside trusted tools.

What Can You Do?

Here’s how to reduce risk immediately:

1️⃣ Audit Installed Extensions

Review all VS Code extensions in your environment. Remove anything non-essential.

2️⃣ Update Immediately

Ensure all extensions are updated to the latest versions. Confirm that Microsoft Live Preview is running version 0.4.16 or later.

3️⃣ Disable Localhost Services When Not in Use

Many of these attacks rely on localhost (e.g., port 5500). Turn services off when they’re not needed.

4️⃣ Restrict Local Network Access

Harden developer machines with:

• Firewall rules limiting inbound/outbound traffic

• Endpoint detection & response (EDR)

• Least privilege access controls

5️⃣ Strengthen Developer Security Policies

• Block untrusted configuration changes

• Train staff on phishing targeting developers

• Monitor for unusual local port activity

Final Takeaway

Extensions are powerful — but that power comes with risk.

A single vulnerable or malicious extension can provide attackers with everything they need to compromise systems, steal sensitive data, and move deeper into your organization.

At Britec, we believe proactive monitoring and controlled environments are key. If your development team relies on VS Code, now is the time to review your extension governance, endpoint protection, and network controls.

Cyber threats don’t just target servers anymore — they target the tools your team uses every day.