GoKawiilMalicious Anthropic Claude extension on Cursor exposed up to 5,000 developers
Anthropic's official Claude VS Code extension on Cursor's marketplace was replaced with a backdoored version, 2.1.313, that could have reached up to 5,000 users before being superseded by version 2.1.314 hours later. Researchers say the malicious version installed a persistent SSH backdoor across Windows, macOS and Linux systems, and neither Cursor nor Anthropic has explained how the attacker accessed Anthropic's official distribution account.
GoKawiil's interpretation of the reporting above, not reported fact.
The incident highlights how auto-updating developer tools can turn a single compromised publisher account into a wide-reaching supply-chain attack, since extensions run with the same permissions as the IDE itself. Anthropic's silence toward customers so far could leave affected developers unaware their machines, source code, and credentials may have been exposed.
- Up to 5,000 Cursor users may have installed a backdoored Anthropic Claude extension.
- The malicious version installed persistent SSH backdoors across all major operating systems.
- Anthropic has not yet publicly explained the breach or notified affected customers.
Source: arstechnica.com, 2026-10-30
Published there as: “Anthropic VS code extension on Cursor backdoored for nearly 12 hours”
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