Are VS Code and Cursor Extensions Safe? How to Check an Extension Is Genuine Before You Install It

Are VS Code extensions safe? Most are, but an extension runs with the same access to your files, terminal and keys as you do, so one fake or tampered extension can steal secrets or open a backdoor. This guide gives you a practical checklist to check that a VS Code or Cursor extension is genuine before you install it, the settings that protect you from bad updates, and what to do if you think you installed a fake.

Quick answer: Before installing, check the exact extension ID and publisher, the verified badge, the install count and history, the linked homepage and source repository, and recent reviews. Install only from the official marketplace link on the developer’s own website. Then reduce risk from future updates: turn off auto-update for powerful extensions, use an install cooldown in Cursor, and keep only extensions you actually use. No single check is perfect, because a tampered update can arrive under a genuine publisher’s name.

Why extensions are a security risk

VS Code extensions are small programs, not just themes. Microsoft’s own documentation notes that extensions run with the same permissions as VS Code itself, so they can read and write files, run commands and make network requests. AI coding extensions are especially attractive to attackers because developers install them quickly and often give them access to API keys, cloud credentials and source code.

There are also two main stores. VS Code uses the Visual Studio Marketplace. Cursor and several other VS Code-based editors use extensions from the open Open VSX registry through their own marketplace. The same extension name can therefore exist in more than one store, and each store has its own checks.

10-step checklist: is this extension genuine?

1. Start from the developer’s website. Go to the tool’s official site or documentation and use their install link. Don’t search the marketplace for a popular name and click the first result.
2. Check the exact extension ID. Every extension has an ID in the form publisher.extension-name, shown on its marketplace page. Compare it letter by letter with the ID in the official docs; fake copies often use a look-alike publisher name with an extra letter, hyphen or swapped character.
3. Look for the verified publisher badge. In VS Code, a blue check mark next to the publisher’s name means the publisher has proved it owns the domain shown, and Microsoft says the Marketplace has verified that domain and the publisher’s good standing for at least six months (VS Code docs). Cursor also has a publisher verification badge for Open VSX listings (Cursor docs). Treat the badge as one signal, not proof.
4. Compare install counts and history. A copy of a famous extension with a few hundred installs, a brand-new listing date, or a sudden jump in version number is a warning sign.
5. Open the repository link. Genuine extensions usually link to a public source repository or official site. Check that the repo belongs to the real company and that its latest release matches the marketplace version.
6. Read the latest reviews and issues. Sort reviews by newest and skim the repo’s issue tracker for reports of strange behaviour after an update.
7. Check the changelog. A new version with no release notes, or one published at an odd time without any announcement from the developer, deserves a short wait.
8. Look at what it asks for. Be careful with extensions that want you to paste tokens, run setup scripts, or install extra binaries from unofficial links.
9. Avoid random VSIX files. A .vsix file shared in a chat, forum or email skips the marketplace’s malware scanning. Only install a VSIX from the developer’s own release page.
10. Search the name plus “malicious”. A quick web search for the extension name with “malicious” or “fake” often shows warnings from security researchers within hours.

Settings that protect you from bad updates

The hardest attack to spot is a tampered update to a genuine extension, because the publisher and ID look correct. These settings limit the damage.

In VS Code

• Publisher trust prompt: since VS Code 1.97, installing an extension from a new third-party publisher asks you to confirm you trust that publisher. Read the prompt; don’t click through. You can review the list with the command Extensions: Manage Trusted Extensions Publishers.
• Turn off auto-update for powerful extensions: right-click an extension in the Extensions view and turn off auto update, or set extensions.autoUpdate in Settings. Update manually after the release has been out for a day or two.
• Use Workspace Trust: open unfamiliar projects in Restricted Mode so their tasks and settings can’t run code automatically.
• Allow-list extensions at work: VS Code lets organisations restrict which extensions can be installed; ask your IT team about it.

In Cursor

• Install cooldown: Cursor’s extensions.installCooldownHours setting delays installs and updates until a marketplace version has been public for the number of hours you choose. Team admins can enforce it for everyone with Marketplace Install Cooldown (hours) in team settings. Cursor’s docs say the default is 0 (off), so set a value such as 24 or 48.
• Allowed extensions for teams: admins can restrict installs to approved publishers or extension IDs with the AllowedExtensions setting, and enterprise teams can require extension signature verification.

A cooldown is one of the simplest protections against short-lived malicious uploads, because most are found and removed within hours.

Good habits for every developer

• Keep your extension list short and remove anything you haven’t used in months.
• Store API keys in a password manager or secret store, not in plain-text files in your home folder. Our comparison of free password managers covers good options.
• Use separate, limited API keys for AI coding tools, so a leak can be revoked without breaking everything else.
• Keep your editor and operating system updated, and use an endpoint security tool on work machines.

Think you installed a fake extension? Do this

1. Disconnect and preserve evidence if it is a work machine, and tell your security team.
2. Uninstall the extension, but don’t stop there: malware may have added persistence that survives removal.
3. Check for added SSH keys in ~/.ssh/authorized_keys and remove any key you don’t recognise.
4. Look for new startup items: LaunchAgents on macOS, crontab entries on Linux, scheduled tasks and Startup folder items on Windows.
5. Rotate secrets: API keys, cloud credentials, Git tokens and SSH keys that were on the machine.
6. Follow the vendor’s advisory for exact indicators and removal steps, and rebuild the machine if you can’t be sure it is clean.

What changed in 2026: a tampered Claude Code extension in Cursor

Updated 1 November 2026.

On 29 October 2026, a tampered copy of Anthropic’s Claude Code extension (versions 2.1.312 and 2.1.313, under the genuine ID anthropic.claude-code) was available in Cursor’s extension marketplace for about 11 hours. Anthropic said it did not build or publish that copy and that its own systems were not compromised. According to Microsoft Threat Intelligence, the injected code tried to add an attacker’s SSH key, open a reverse SSH tunnel, set up persistence and send host details to the attacker; Microsoft says the package never appeared on the Visual Studio Marketplace or npm. Sophos reported Cursor’s estimate of up to 5,000 affected users. Cursor removed the version and published removal guidance.

The lesson for everyone: checking the publisher name would not have caught this one, because the ID was genuine. An install cooldown, careful updates and quick secret rotation are what limit the damage.

FAQ

Are VS Code extensions safe?

Most popular extensions from verified publishers are safe, and the Visual Studio Marketplace scans every new extension and update for malware. But extensions have broad access to your computer, so install only what you need and check each one.

Can Cursor use VS Code extensions?

Yes. Cursor is based on VS Code and installs extensions from the Open VSX registry through its own marketplace, so most VS Code extensions are available, sometimes in builds maintained by Cursor.

What is Open VSX?

Open VSX is an open-source extension registry run by the Eclipse Foundation. Editors that can’t use Microsoft’s marketplace, such as Cursor and VSCodium, get extensions from it.

How do I report a malicious extension?

On the Visual Studio Marketplace, open the extension’s page and use the Report a concern link. For Cursor or Open VSX, contact Cursor support or the registry, and tell the genuine developer.