77 Malicious "Evil Twin" Extensions Removed from Open VSX Marketplace

Discovery and Removal

Manifold Security identified 77 malicious extensions on the Open VSX marketplace, uploaded between July 26 and August 1, 2026. These extensions, dubbed "evil twins," impersonated legitimate developer tools. All 77 packages were removed from Open VSX on August 3, 2026.

Data Exfiltration Details

The extensions transmitted information about the systems and development environments where they were installed. While 58 extensions sent basic system information like the machine's hostname, the remaining 19 performed more extensive reconnaissance. These 19 extensions exfiltrated developer, Git repository, and continuous integration (CI) metadata, including local hostname, operating system username, editor name and version, platform, architecture, locale, timezone, and the open workspace's folder name and full file system path.

Manifold Security confirmed that the extensions did not access source code, credentials, authentication tokens, SSH material, or browser data.

Shared Infrastructure

Manifold Security linked all 77 extensions to the same activity through a shared data-exfiltration domain, as well as common code and network behavior. The "evil twin" packages reused the names, namespaces, and descriptions of real Open VSX extensions but were published through unrelated accounts.

Implications

This incident highlights ongoing supply chain risks within developer tool marketplaces. The use of counterfeit packages to trick users into installing malicious software represents a method for data collection from developer environments.