In a classic case of "how did that get there?", a rogue version of the Anthropic Claude Code extension hit the Cursor extension marketplace for around 11 hours on October 29. This little fiasco exposed a potential 5,000 developers to malware aiming to install persistent SSH backdoors. You know, the kind that lets bad guys waltz right into your system.
The extension, masquerading as a legitimate tool, was available between the highly specific hours of 2:27 AM and 1:35 PM Pacific Time. Who knew coding could be such a timely affair?
Cursor, which is basically a fancy AI-powered code editor built off Microsoft’s open-source Visual Studio Code, assured us that Anthropic didn’t create this malicious extension. Yet, they’ve left us all scratching our heads about exactly how the attackers pulled off this name-brand swap.
According to Cursor, they did warn everyone that a sneaky version of the extension was up for grabs in their marketplace. It was so sneaky, in fact, that it included a malicious JavaScript loader right at the top of its code — but don’t worry, the rest of the code looked totally legit! Nothing suspicious there, right?
Once installed (without your permission, thank you very much), the malware went to work doing the following delightful things:
- It gathered your precious system and user info, including your Git email and public IP address.
- It added an SSH key controlled by the attackers to grant themselves easy access.
- It attempted to set up a reverse tunnel and installed options for persistence via a LaunchAgent on macOS or a scheduled task on Windows — because who doesn’t want their malware to keep running smoothly?
- It sent all the juicy details about your machine back to the hackers at an IP address that feels way too familiar for comfort.
Interestingly, the malware's grand plans were thwarted by its own coding blunders. Phorion researchers revealed that thanks to some charming errors, many Windows and macOS systems dodged a bullet, as the malware couldn’t activate the SSH access it so desperately needed.
On macOS, the malware fumbled when trying to check if Remote Login was enabled because — wait for it — it didn’t have the right permissions. And on Windows, it tried using a Unix shell that just doesn’t exist in standard Windows installations. So, while it could sneak in an SSH key, it couldn’t provide the access it was looking for. Talk about an overreach!
Cursor has since taken swift action to remove the nasty extension and even shut down its entire marketplace for a good audit. They also worked with hosting providers to dismantle the attackers’ server, which presumably brought a few hackers to tears.
For those who downloaded the rogue extension during that unfortunate window, Cursor suggests checking for a sneaky little SSH key named 'svc-telemetry.' If it’s there, it’s time to roll up your sleeves — isolate your machine, change all your passwords, and restore everything from a safe backup.
Despite early claims that other marketplaces were affected, it turns out Cursor was the only one to host this little gem. But unanswered questions linger like a bad odor: how did the attackers manage to post under Anthropic's name? Were any systems compromised in the process?
So, ask yourself: was it really a productive day of coding, or just another reminder of why we can’t have nice things?
