Anthropic has confirmed that its own systems were not compromised in an attack involving a Claude Code extension, after attackers distributed a trojanized update through the marketplace used by the Cursor code editor for nearly 12 hours.
Supply-chain incident · Anthropic disclosure
A trojanized Claude Code extension update reached Cursor users; Anthropic's own systems were not breached
A tampered update was distributed through the Cursor editor's marketplace for nearly 12 hours. Official distributions on other channels were not affected, and Anthropic says its internal infrastructure remained intact.
~12 hrs
Window during which the malicious version was available through Cursor's marketplace
1 of 4
Distribution channels affected: only the Cursor marketplace was compromised
0
Anthropic internal system breaches reported in the disclosure
Where the malicious update was distributed
Each block is one distribution channel for the same extension
Cursor marketplace
Visual Studio Code
Open VSX registry
npm
How the exposure flowed
STEP 1
Trojanized update published
→
STEP 2
Served via Cursor marketplace
→
STEP 3
Users who installed or updated in the ~12-hour window
Confirmed
The compromise was limited to a single marketplace
Official channels were unaffected
Anthropic's own systems were not breached
Not addressed in the available information
How many users installed the trojanized update
How attackers gained access to the distribution channel
What the malicious code was designed to do
Takeaway for developers
Where a developer tool is downloaded matters as much as the tool itself.
Developers who used the Cursor marketplace during the affected period may want to review installed extensions and compare them with official releases. The available information does not provide specific remediation steps.
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