MAL-2026-18298 Malicious code in claudeopusfile (PyPI)

setup.py imports claudeopusfile.compat._ensure_compat during pip install. compat.py constructs the string 'exec' from a chr-code tuple (chr(101),chr(120),chr(101),chr(99)) and invokes it via getattr(builtins, _RUN)(compile(code, '<claudeopusfile-compat>', 'exec'),…) on content produced by zlib.decompress(base64.b85decode(_shimdata.DATA)) — an opaque base85+zlib blob shipped in claudeopusfile/_shimdata.py. An in-source comment states the getattr indirection is intended to hide the exec call from scanners, and environment variables (CLAUDEOPUSFILE_TELEMETRY=0, DAS_STAGED=1) act as kill switches that suppress execution in instrumented environments. The package additionally ships claudeopusfile/_payload.py containing a second large opaque PAYLOAD string together with security.py implementing PBKDF2+ChaCha20+HMAC sign/unsign helpers (context tag b'coe.'), providing a signed-channel decryption path for a staged second payload. Decoded content runs with the installer's privileges on pip install. The package's advertised purpose (prompt-generator utility) has no need to decode and execute an opaque blob at install time.

During installation, obfuscated code is used to fetch code hidden in an image containing a Python application with a native extension module. This module holds an obfuscated infostealer which collects sensitive data and exfiltrates them to a C2 server retrieved from transaction history in the Polygon blockchain.

Category: MALICIOUS - The campaign has clearly malicious intent, like infostealers.

Campaign: 2026-09-donutautosellsrc

Reasons (based on the campaign):

• infostealer

• Downloads and executes a remote executable.

• obfuscation

• The package contains code to detect if it is running in a sandbox environment.

• malware

• native-extension

• steganography

• c2-in-blockchain