Flaws in popular VSCode extensions expose developers to attacks

Source: Bleeping Computer

Vulnerabilities with high to critical severity ratings affecting popular Visual Studio Code (VSCode) extensions—collectively downloaded more than 128 million times—could be exploited to steal local files and execute code remotely. The security issues impact Live Server (CVE‑2025‑65715), Code Runner (CVE‑2025‑65716), Markdown Preview Enhanced (CVE‑2025‑65717), and Microsoft Live Preview (no identifier assigned). Researchers at application‑security firm Ox Security discovered the flaws and attempted disclosure in June 2025, but received no response from the maintainers.

Remote code execution in IDE

VSCode extensions are add‑ons that expand the functionality of Microsoft’s integrated development environment (IDE). They can add language support, debugging tools, themes, and other customizations, and they run with significant access to the local development environment—including files, terminals, and network resources.

Ox Security published reports for each of the discovered flaws and warned that keeping the vulnerable extensions could expose corporate environments to lateral movement, data exfiltration, and system takeover.

• Live Server (CVE‑2025‑65715) – The extension has over 72 million downloads. An attacker exploiting this critical vulnerability can steal local files by directing the target to a malicious webpage.
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• Code Runner (CVE‑2025‑65716) – With 37 million downloads, this vulnerability allows remote code execution by changing the extension’s configuration file. An attacker could trick a user into pasting a malicious snippet into the global settings.json file.
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• Markdown Preview Enhanced (CVE‑2025‑65717) – Downloaded 8.5 million times, this high‑severity (8.8) issue can be leveraged to execute JavaScript via a maliciously crafted Markdown file.
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• Microsoft Live Preview – Versions before 0.4.16 contain a one‑click XSS vulnerability that can be exploited to access sensitive files on a developer’s machine. The extension has more than 11 million downloads.
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The flaws also affect Cursor and Windsurf, AI‑powered VSCode‑compatible alternative IDEs.

Ox Security’s report highlights that threat actors leveraging these issues could pivot across networks and steal sensitive details such as API keys and configuration files.

Mitigation recommendations

• Avoid running localhost servers unless necessary.
• Do not open untrusted HTML while a local server is running.
• Refrain from applying untrusted configurations or pasting snippets into settings.json.
• Remove unnecessary extensions and install only those from reputable publishers.
• Monitor for unexpected changes to extension settings.