Bloom Security Exposes Supply Chain Flaws in VS Code and Open VSX Ecosystems

A new investigation by cybersecurity firm Bloom Security has highlighted a security gap in integrated development environments, detailing how missing extension references can leave popular coding platforms exposed to supply-chain attacks. The research, titled "Extension Resurrection," demonstrates how malicious actors could register abandoned or nonexistent extension namespaces inside legitimate extension bundles hosted on Microsoft's Visual Studio Code Marketplace and the Eclipse Foundation's Open VSX registry.

The vulnerability relies on what Bloom Security calls "shadow dependencies." When an established extension pack references a component that is absent from the marketplace catalog, the associated namespace remains available. An attacker can subsequently register that open name and upload a payload. Because end users have already authorized the primary extension pack, the platform automatically downloads and executes the newly registered dependency alongside the rest of the bundle.

According to research details published by The Next Web, the exposure affected a notable portion of the developer ecosystem. Bloom Security identified 677 out of 4,179 analyzed extension packs on the VS Code Marketplace that contained at least one missing reference. Similarly, 94 out of 321 packs inspected on Open VSX contained vulnerable references. Combined downloads for the affected packs exceeded 500,000.

The threat is magnified by the platform's automatic update mechanisms. Extension packs generally do not pin bundled dependencies to specific version numbers. As a result, an engineering environment running a legitimate pack installed months or years in the past could silently receive a newly registered dependency during an automated update, without requiring any fresh action from the developer.

Security analysts noted that compromised extensions carry significant privileges within developer workstations. Extensions executing in VS Code and compatible environments—such as Cursor, Kiro, Windsurf, Antigravity, VSCodium, and Eclipse Theia—run with Node.js host privileges. This level of access enables them to read and write local files, launch background processes, and establish outbound network connections.

Bloom Security disclosed the findings to both ecosystem operators. The Eclipse Foundation received notification regarding Open VSX on February 5, 2026, moving quickly to secure open namespaces and institute checks for missing dependencies. Bloom Security notified Microsoft regarding the VS Code Marketplace on February 17, 2026. Microsoft initially classified the risk as Moderate before reopening the case upon reviewing further evidence from Bloom Security, ultimately rolling out protections in phases that included admin-level safeguards in October 2025 and user-level mitigations completed in June 2026.

The findings underline a growing systemic risk in software engineering infrastructure, where developer extensions are frequently deployed without the same scrutiny applied to standard software packages. Security experts advise enterprise teams to extend monitoring to IDE environments, maintaining active inventory control over installed plugins, configuration settings, and automated update behaviors.