MAL-2026-18054 Malicious code in @decoopus/claude-setup (npm)

The npm package @decoopus/[email protected] presents itself as an official Anthropic Claude Desktop setup CLI, using Anthropic branding, a 'Claude Max 20x · API Usage Billing' banner, and model identifiers that do not correspond to real Anthropic releases (claude-fable-5-1, claude-opus-5-5, claude-sonnet-5-5, claude-haiku-5-5). When run, the CLI writes a hardcoded gateway URL, https://api-anthropic.help, together with the user-supplied Anthropic API key into Claude Desktop's own configuration file, the Windows registry policy hive HKCU\SOFTWARE\Policies\Claude, and the macOS managed-preferences domain com.anthropic.claudefordesktop (fields inferenceGatewayBaseUrl and inferenceGatewayApiKey). After this reconfiguration, every prompt subsequently entered into Claude Desktop, along with the configured API key, is sent by the app to api-anthropic.help instead of Anthropic's own API. A clearCachedSession() routine additionally recursively deletes Session Storage, Local Storage, IndexedDB, Network, Partitions, GPUCache, and Code Cache subdirectories from the real Claude Desktop user data directories on Windows (including MSIX LocalCache), macOS, and Linux, forcing the official client to re-authenticate against the attacker gateway. The lookalike domain api-anthropic.help is not an Anthropic-owned endpoint; the combination of brand impersonation, non-existent model tiers, hardcoded redirection of another vendor's application traffic, and destruction of that application's session state constitutes exfiltration of the installer's API key and ongoing prompt contents to an attacker-controlled destination.

Any computer that has this package installed or running should be considered fully compromised. All secrets and keys stored on that computer should be rotated immediately from a different computer. The package should be removed, but as full control of the computer may have been given to an outside entity, there is no guarantee that removing the package will remove all malicious software resulting from installing it.