Fake Claude Code Plugin in Cursor Store: 5,000 People Affected

The fake Claude Code add-on was uploaded to 5,000 people in Cursor's VS Code add-on store. The plugin attempts to install a persistent SSH backdoor.

The fake Claude Code add-on was available in Cursor's VS Code add-on store for about 11 hours. Cursor also shared the incident as an important security announcement for its users. The company announced the issue in an official statement dated October 29. Accordingly, 5,000 people installed the add-on.

When Was the Fake Claude Code Plugin Released?

First of all, Cursor's description clearly states the hours the malicious version remained in the store. The fake Claude Code add-on was live between 02.27 and 13.35. Therefore, a period of approximately 11 hours is mentioned. Additionally, the number of people who installed the add-on reached 5,000 in this period.

The plugin in the store is a maliciously modified version of Anthropic's Claude Code plugin. However, Anthropic did not develop this version. Moreover, this situation is clearly emphasized in Cursor's statement. Therefore, the plugin installed by users is not Anthropic's own work.

The basic information of the event is as follows:

Number of people affected: 5,000

Hours when the malicious version remains on air: Between 02.27 and 13.35

Announcement date: October 29

Purpose: attempt to install a permanent SSH backdoor

Published in: Cursor VS Code plugin store

What Does Persistent SSH Backdoor Mean?

SSH is a method used to connect to computers remotely and encrypted. Additionally, a backdoor is a secret way that allows an attacker to access the system by bypassing normal login steps. On the other hand, the expression permanent means that this road is not temporary and is intended to remain open for a long time.

A plugin is a small piece of software that adds new features to the code editor. The store is also where these software are installed with one click. Therefore, a modified version of a plugin in the store poses a separate risk for users.

Additionally, according to Cursor's statement, the fake Claude Code plugin runs malicious code. This code tries to install the SSH backdoor. Moreover, the statement in the description shows that the plugin not only poses a risk, but also actively runs code. Therefore, it becomes a security issue for people who install the plugin.

What's Next for Cursor?

Cursor was recently purchased by SpaceX for $60 billion. However, the security announcement came shortly after this purchase. However, the focus of the announcement is the fake Claude Code add-on in the store.

The most important point for users is the loading time. Because those who installed the Claude Code add-on between 02.27 and 13.35 may have encountered the modified version. At the same time, the statement states that the number of people who installed the fake Claude Code add-on is 5,000. Therefore, the next stage of the process will be between the Cursor and the users.

Finally, Cursor stated that it would contact users who downloaded the add-on regarding the situation.